Boss in Mook Clothing

""Let's be very careful here. We don't want to see him...(pwooow, pwooow) Uhhh, oh no! IT'S HIIIIM.""

- "Final Fantasy (NES) RMSCRT part 17a of 19"

Mooks in video games typically aren't supposed to be too hard on their own. They are usually just there to soften up the heroes before the Boss Battle of a level. But there are exceptions, enemies that are annoying, dangerous, and/or powerful. This trope is the top tier of these, which are enemies that are so powerful, you wouldn't be blamed for mistaking them for bosses (hence the trope name).

For example, let's say you are playing an Eastern RPG. You're walking along on your quest to save the world, when you run into a Random Encounter with a three-headed, skeletal dragon. Okay, you're 12 levels higher than the average enemy here, so just give it a few attacks, and it should be over with.

But not only is it still standing after three turns, but most of your party has lost over half their health. So you don't hold back. You launch your best spells and special attacks at it, using your healer's super expensive full party heal spell. Eventually, it goes down, but not before you had to resurrect the mage twice, and you had to use up two-thirds of your total magic point pool. Time to warp to the nearest Trauma Inn.

In order to determine if a regular enemy qualifies, it must have at least two of the following traits. It can be any of these traits, but it must have two or more.
 * It has A LOT more HP than a regular enemy.
 * Can also have extremely high defense or evasion (similar to a Metal Slime, and may even cross over with one) if such stats exist.
 * It does a lot more damage than a regular enemy (moot if the protagonist is a One-Hit-Point Wonder) and is quite capable of Total Party Kills.
 * Can also have attacks that are difficult to avoid (moot if it's a game where dodging is based on chance, like a turn-based RPG).
 * Tend not to miss, even in the games where you can improve your dodge chances.
 * Requires a lot more strategy to defeat than a regular enemy. (The Useless Useful Spell is almost certainly useless here, unless used as an Outside the Box Tactic.)
 * Has at least one of the following points, but one of the above must still be included to count:
 * Has a lot of varied attacks compared to regular enemies.
 * Has the ability to inflict many Standard Status Effects on you, sometimes multiple effects at once.
 * Has an entrance like a boss or mid-boss, but is not in a designated Boss Room and/or has no Life Meter.
 * Does not respawn the first few times you meet it (assuming the game has respawns), but is still not in a designated boss area.
 * Gives you either a lot of rewards for your effort or barely any at all.
 * Appears by itself, or with a few small enemies that can be wiped out easily.

Compare Smash Mook, That One Boss, Demonic Spiders, Kung Fu-Proof Mook.

Contrast Goddamned Bats, King Mook, Mook Promotion, Anticlimax Boss, Degraded Boss, Level in Boss Clothing.

Not to be confused with Bonus Boss or Bitch in Sheep's Clothing.

Before Editing: Check to see if Demonic Spiders or King Mook is a better fit for your example

Action Adventure

 * The Guardian (also known as the Final Guard in later games) from Castlevania: Symphony of the Night. They protect the room to Dracula (poorly, since there is the way below), but they are still really tough to beat (barring Game Breaker methods).
 * And the Cthulhu when you first encounter it in the Marble Gallery. They only guard a way back to the entrance but they are very difficult at this point in the game. They are easy when you encounter them in the  though, since this much later in the game.
 * Victory Armor from Harmony of Dissonance. It's a pushover when you meet it just before Death, but until then, watch out.
 * The Devil from Circle of the Moon.
 * Rondo of Blood has a few. There is an armour type knight very similar to the later Guardian that can do heavy damage. In one level, there are two at once, in a tiny room with little breathing room. Better hope you have enough hearts to item crash!
 * In Stage 5, there is a painting that moves. If you get hit by it, it somehow catches you and then snaps in half, instantly killing your character. Just keep attacking it from a distance as it flies around the room or you're fucked.
 * Darknuts and Iron Knuckles are frequently like this, when they aren't used as bosses or mini bosses themselves. Both The Legend of Zelda Twilight Princess and The Legend of Zelda the Wind Waker feature Multi Mook Melees that end in fights against three Darknuts, and they're arguably more difficult than the final bosses. (However, in Twilight Princess, if you have the Magic Armor that eats money, you're pretty well set.)
 * Or Wind Waker's Magic Armor that eats magic, and a few blue or green potions...
 * Twilight Princess does use a Darknut as a miniboss, it's widely considered a Best Boss Ever, given that you can unleash your full arsenal of moves against it.
 * The Alpha Sections in Beyond Good and Evil; not to mention that they're everywhere. While they do have a multitude of weaknesses and tricks that can be used to take them out easily, taking them head-on is almost guranteed to end in your ownage. They have mines, lasers, and hammers that deal tons of damage, and they have shields that make them extremely hard to hit. Luckily, you can sneak past them most of the time.
 * The Dust Men mecha conduits in In Famous are two stories tall, have attacks involving chucking fiery projectiles the size of cars and an equally fiery gattling gun, and are armored HP on legs that take a good five-to-ten minutes to kill. The first time you see one, you fight it alone on an empty field...but after that, they populate the game world, and are often surrounded by boatloads of other enemies and distractions. One particularly harrowing Hold the Line mission involves fighting off two at once while two dozen other Dust Men pepper you with gunfire around them.
 * Blue Dragon, the Aquamantis homage from Three D Dot Game Heroes. It does ridiculous amounts of damage and can take a few hits to boot. The good news is it rarely shows up, the bad news is it can show virtually anywhere.

Action Game

 * The Alto Angelo armors in Devil May Cry 4. Tough, fast and hard-hitting, almost always in packs with their Bianco Angelo lesser versions. Fortunately, there is an exploit to clean house fast, and paying Homage to Zangief with the Devil Triggered Buster against them is always a satisfying payoff.
 * And the Shadow monsters in the original Devil May Cry. While not quite as difficult as the actual bosses (most of which are That One Boss), they qualify in every other respect and would be difficult bosses in most games.
 * Devil May Cry 4 also has the Blitz enemies. Spends most of it's time encased in a lightning shield which hurts Dante/Nero should they melee attack them whilst it's up, leaving you to spam the weak ranged moves to get rid of the shield. They also love to teleport around the arena in a ball of lightning, are invincible whilst doing so, and will appear and strike without warning, sometimes right in front of you. Thankfully in story you only have to deal with one at a time, but in the Bloody Palace survival mode, you have to deal with 2 at once. The only thing that makes these guys even slightly easier is that because they're blind they sometimes attack anything that fights in the room. Then if you take them down to a certain evel of health, but don't do enough damage to finish them them during their shield down phase, it Turns Red and in addition to normal attacking at even greater speeds, will find great joy in trying to spear you with their horns, and blow up with you impaled on them (thankfully, like all DMC grabs, this can be broken by entering DT mode).
 * Devil May Cry 3 inverts this with the Hell Vanguard. Initially, you fight him on level two as a proper boss fight. Some stages later, Hell Vanguards appear regularly in the middle of levels as if they're regular foes. In some instances, you fight two of them at once, and Hell Vanguards are not the kind of enemy you want to fight two-on-one. In Bloody Palace mode, there are levels where you can fight three of them at once. When a game turns an earlier boss into an Elite Mook for kicks, you know it wants to murder your ass.

Beat'Em Up

 * In God Hand, sometimes, when you kill an enemy, a demon jumps out. Now normally these are no rougher than the standard Giant Mook, although they can really suck if you're low on health. But after Level Four, there is a chance that when you kill an enemy, one of the Four-Armed Demons will emerge. The first one you met in the game got its own cutscene. They have a beam attack, deal great damage, and carry a massive trident. If at all possible, run for your freaking life.
 * Similarly, the Sensei. Like demons, these samurai-wannabes have unique health bars and the first one got a cutscene. Deadly reach, pretty damn resilient and powerful. Consider them a That One Boss Preview - if you have difficulty with them, their Old Master, the Great Sensei, will eliminate you with very little effort.
 * Bayonetta has the enemy duo known as Gracious and Glorious. While they don't have a huge amount of health or hit extremely hard, they make up for it in sheer speed: the two of them can easily hit and combo you, and it's difficult to keep pummeling them even after you've gotten some solid hits in because they can break out of your combos so easily. To make matters worse, it's impossible to use Witch Time against them through normal methods. Oh, and expect to face off with Gracious and Glorious more frequently on Hard difficulty and above.

First-Person Shooter

 * Hunters in the Halo series. Also to some extent the Gold Elites in the first game (which slice and dice your Redshirt Army) and the Silver Ultra ones in the second. Especially in the Mausoleum, aka "Breaking Benjamin Room" Multi Mook Melee.
 * In the first Halo once one knows how to deal with them the Hunters become ridiculously easy, especially evident on the hardest difficulty, where even the lowliest Elite is a dangerous threat. Simply get close to the Hunter, wait for it to try to melee, dodge and circle around to its back and put a single pistol or shotgun round into the exposed flesh For Massive Damage. Brought them down in a single stroke. They fixed this in the next game, where Hunters have an attack designed specifically to crush players standing directly behind them.
 * By Halo Reach Hunters had reached some sort of boss in mook clothing nirvana. They take ridiculous amounts of ammunition to kill, are near impossible to get behind no matter how much you run, jump or even jetpack over them, their attacks are near one hit kill on Normal, and one hit kill by Legendary, they are faster, tougher, and quicker. The best bet is literally to sit as far away as possible and rocket spam them, which isn't always an option. Even going up behind them and shooting their exposed backs with the shotgun takes 3-4 hits on Heroic, and more on Legendary. And since they'll turn around and take Extreme Melee Revenge on you as soon as you fire once, and your shotgun is pump-action...Even plasma grenades are significantly reduced in effectiveness, because the Hunters can catch them on the shield.
 * In Bioshock, certain machinegun-wielding enemies in Apollo Square have as much or MORE health as the game's major bosses, but are otherwise completely undistinguishable from the regular machinegun-wielding enemies who have much less health.
 * Leadhead splicers are supposedly resistant to bullets, so other weapons should still be effective.
 * Then there is the matter of 'Rose' a spider splicer with several times more health than other spider splicers
 * The Shamblers in Quake. Nightmare Fuel-errific Yeti-type monster with a ton of HP, resistance to stunning and explosive damage, and a lethal line-of-sight lightning attack, similar to the Archvile's flame attack in Doom II. The spideresque Vores too, which appear as a sort of Mini Boss at the end of the second episode. Their homing exploding spiked ball attack is nigh-impossible to dodge, and would chase you at high speed through winding corridors. You had better know the level like the back of your hand and hope you don't run into any obstacles.
 * From the Doom series:
 * Arch-Viles from Doom II. They have a very powerful flame attack that does heavy damage if you're in their line of sight when it finishes, and they can resurrect dead monsters as often as they like, with the exception of Cyberdemons, Spider Masterminds, and of course other Arch-Viles. Oh, and their toughness is approaching 3/4 that of a Baron of Hell, two of which showed up as the Boss Battle of Doom's first episode before showing up as a Degraded Boss in various levels in Doom and Doom II thereafter.
 * Thankfully though they do have a maximum range, and are unable to attack if you're over a certain distance away. Unless you hit them first, in which case they will retaliate against your aggression.
 * The stand-alone source port mod Scoredoom has quite a big variety of these type of enemies, with many of the superboss enemies (each one having 6000 hitpoints, with the Superdemon having only 4000) being much worse than the UDoom Endbosses.
 * Hell Knights in Doom 3 are that particular game's answer to the Barons of Hell. And just like the original, you fight a pair of them before warping into hell. This time, you probably have the BFG, although you lose it shortly after.
 * Bruisers in Resurrection of Evil - take a Hell Knight, cross him with a Mancubus, and then stand the hell back.
 * Quake II and Quake IV had the Tanks, which themselves have an Elite Mook variation, Gladiators, Harvesters, Iron Maidens(Q4), Stream Protectors, Heavy Hover Tanks(Tank plus Assault Commander from Duke Nukem 3D), etc. One room near the end of Q4 is a Multi Mook Melee with these types of enemies.
 * The Super Tank, and the Hornet/Tankflyer, which may be considered King Mooks that reappear as Degraded Bosses.
 * The Quake III Arena Mod "Hunt" subverts it a little by having no actual bosses. But out of the three types of monsters, the Titans are definitely the closest thing you can get. (Though they are complete raving lunatics and will attack their own team, including other Titans). The best strategy for these guys is to snipe from afar or to hit them with the BFG. The mod itself is so customizable that it's simple to make EVERY SINGLE ENEMY like this.
 * The Q4 version of the Gladiator was probably the worst regular enemy in that game, other than maybe the Heavy Hover Tank. Made of Iron, Deflector Shields, deadly Super Nailgun, and its railgun was a lot more unpredictable and harder to dodge. And it only deactivates its shield when it's about to fire the railgun.
 * Purr-Linn Juggernauts and Mantid Soldiers in Turok 2. Both are Made of Iron, have small weak points, and attack with deadly plasma bolts. The former are also Demonic Spiders, due to their unusual agility for their size.
 * Voltigores in Half Life: Opposing Force. Giant Race-X monsters with ungodly health, incredibly powerful electrical attacks with area of effect damage, and the ability to self-destruct upon death. Late in the game, you come up against a massive horde of them, in a completely black sewer tunnel.

Hack and Slash

 * Bujingai the Forsaken City has several minibosses in the forms of demonic "Overlords" of Tears, Sin, Despair, and Pain. They look like basically any other demon, except for the facts that they're the only enemies aside from the final boss to have a counter meter like you do and that whenever you see one you're immediately trapped in that area.
 * The Oblivion Knights in Diablo 2 and the minions of Destruction in the expansion. The first acting a lot like a boss would: commanding large armies of minions while bombing you with powerful attacks and curses, while the second is powerful enough to take out a player character 1 on 1. Yes, both are normal creatures. God help you if you meet a unique variant (and you WILL). Luckily, they only appear directly before the boss battle of their respective acts.
 * Interestingly in the first game, Diablo himself, the final boss of the game, is treated as a regular mook known simply as "The Dark Lord".

MMORPGs

 * World of Warcraft has its own classification for such monsters: elite. While those monsters mostly show up in dungeons geared for a group of player capable to deal with them, but some of them are found in the open world and can quickly kill unsuspecting players. The three most infamous examples:
 * WANTED: HOGGER - Woe to any newbies who think he is just your average level 11 gnoll!
 * This low-level mob's fearsome reputation has been immortalized in the recent expansion. Not only is he a memory alongside raid and dungeon bosses you may fight during one encounter, he now has his very own statistic tracked by the game: Deaths by Hogger.
 * Hogger got so famous that he lost this trope. In Cataclysm, he was moved and is the new endboss of the Stormwind Stockade dungeon. This effectively turns Hogger into a King Mook.
 * Devilsaurs, T-Rex-like enemies that patrol an entire zone. Unlike other giant enemies, their movement isn't easy to hear, earning them a reputation of being sneaky.
 * Sons of Arugal, scoring bonus points for looking a lot like regular enemies in the same area, but being as tough as their brothers found in a nearby dungeon. And being ten levels higher than anything else in the area. Fortunately, their numbers were cut back somewhat in a patch.
 * Fel Reavers, being seventy-feet tall mechanical constructs that blot out the horizon, sound like a freight train piling into a factory of tubas, and shake the landscape for yards around with every step. They seem about as stealthy as a sumo wrestler wearing full plate mail trying to tiptoe through a room of sleeping cats, but just you try and sit down and rest for a moment in the Hellfire Peninsula without experiencing that dread moment of looking behind you only to see an eclipse of black metal and green fire just close enough to ruin your day. As an aside, for a brief period during the beta, the Fel Reavers' models accidentally switched to that of a regular bear; with predictable results. More than a few lives were lost to the dreaded Bear Reavers.
 * Their scream is like a hellish pig squealing through Pink Floyd's concert microphone system. You never forget the first time you hear that scream as you start wondering why the ground is suddenly shaking...
 * Another classification of monster is "rare", which only spawn once every several hours, can (usually with the higher levelled ones) take a concentrated group effort to down, and act as mobile loot pinatas. Rares are distinguished by the smaller silver dragon around their portrait. Finally, you can combine both types into the "elite rare" class, which has a big silver dragon around its portrait and usually a necklace of player skulls around its neck...
 * The Storm Giants that patrol Howling Fjord may also count. Thankfully, they have very loud footsteps, so you can at least hear them coming from a long way off.
 * Giants tend to be this in general. Especially dangerous are Sea Giants, mostly because they're arguably the most common type of giant. There are a quite a few wandering around Desolace, probably one of the first times you'll see them. But the waters of Feralas and Tanaris have veritable armies of them patrolling the depths and beaches.
 * Garginox, the flesh giant in the Eastern Plaguelands. He patrols a single area for no apparent reason other than to screw players over. He's got nearly 28000 health and has dungeon endboss-like damage output. Worse, the area he's in is a questing area, and if you happen to be looking in the wrong direction, turns out he's much quicker and quieter than his mountainous size would imply.
 * EverQuest was so full of this trope it had its own name: the dreaded undercon. Monsters way more powerful than their level (shown prosaically through the /consider command) indicated, many a newbie and soloer have died to undercons over the years. In the game's early days almost every mob was an undercon after level 20, meaning that unless a player was a dedicated solo class, they had to group to progress.
 * Holly Windstalker was a particularly notorious example. Not only did she undercon, but she appeared to be a friendly, fairly weak NPC innocently wandering a low-level zone. She would also immediately aggro if the character was an "evil" class or caught harassing the local wildlife (which the zone was full of, most of them aggressive on their own), making her this trope, a Wake Up Call Boss and That One Boss all combined. Her nickname was "the bitch" for a reason.
 * Ultima Online had a fair amount of these. Their were a limited number of sprites for monsters and many monsters used the same sprite with a palette swap. For instance, one player could handily dispatch an air elemental. A team of experienced players could take down a blood elemental. An acid elemental was a sort of walking nuke and would occasionally kite a player into the wilderness where it would slaughter unsuspecting travelers and haunt the dreams of children until the server reset.
 * Likewise, their were at least four different creatures that used the demon sprite, ranging from minor demons that weren't especially horrid, to the Balron (not to be mistaken for the similar yet totally distinct Balrog), which had one of the highest hit point totals in the game and could outrun a mounted player in a straight run. Which didn't stop someone from soloing them for fun. While riding a Llama.
 * All over the place in Maple Story, as well as Fluffy the Terrible, as most enemies look either harmless, cute, or similar to another enemy. There are often also one or two much more deadly enemies in areas filled with more level friendly enemies. This would be a lot less Egregious if there was a way to tell how strong an enemy is in-game other then letting it hit you.
 * They fixed this, sort of. You can either click on it to open the book to sort of gauge its level, or you can attack it, know for sure what level it is, then get killed because you pissed it off.
 * They have totally fixed it, as attacking an enemy now shows its HP Meter, name, and level, along with a coloration of its name. Yellow means it's more than 20 levels lower than you (too weak to even bother killing, as there is an EXP penalty for killing a monster more than 10 levels lower than you); white indicates a monster within 20 levels of you, either below (the closer to you the better most of the time) or above (usually still okay until the difference is at least 7 or 8); red is for monsters more than 20 levels higher than you (run). Needless to say, you will sometimes die because that little furball in Leafre was around level 100 and you didn't realize it until you attacked.
 * Warhammer Online loves this trope. Fighting a bunch of nameless mooks? Well odds are there will be one in that pack wandering around somewhere who is a champion which means many more HP and hits a lot harder. They also tend to be physically identical to the nameless mooks.
 * Gaia Online's MMO zOMG! has the Mask of Death and Rebirth enemies in the Ruins. As you attack a Mask, it cycles through three forms, each of which happily spams Eye Beams to inflict you with Standard Status Effects crippling gameplay. It has a gigantic health meter. Use Iron Will? Even at RR 4, that damn mask can overcome your resistance buffs. Bring friends? So did it. You basically need a full crew to battle Masks. And not only do they spawn in areas you need to go through to finish the area plot, but the area plot itself includes a farming quest for Jewel Eyes. Have fun with that!
 * Battle Stations features a few of these. When exploring, a higher level player may encounter such enemies as the Royo Skycutter or worse, the Hydra. These creatures are almost impossible to beat by players in the level ranges for which they appear.
 * The Stone Summit mobs in the elite dungeon Slaver's Exile of Guild Wars. Unlike the haphazard build of many enemies, these have strong and coordinated builds with multiple resurrection skills. On top of that, they possess all the usual monster perks like having effectively infinite energy and being almost half again your level, reducing the damage they take and increasing the damage you take.
 * Expanded with the Guild Wars: Beyond updates. New questlines introduce new mooks throughout Cantha and Kryta who have the same perks as the Exiled Stone Summit.
 * For that matter, ArenaNet's definition of "boss" means that many of the final bosses in campaigns and dungeons are easily mistaken for regular mooks. They are deemed "boss-like foes", which means while they enjoy all the perks of being a boss (double damage and unique abilities), the player cannot copy their skills and they lack the signature boss aura.
 * Kingdom of Loathing has the Baiowulf, which is an Ultra Rare encounter, and the only thing in the game which drops the incredibly valuable Talisman of Baio. It also has triple the stats of any other encounter in the area. It's still a pushover if you're backtracking, but encountering it when you first unlock the area means you're likely to get beaten up by it.
 * Perfect World seems to love dropping the occasional level 100 monster in relatively low-level areas.
 * Atlantica Online's dungeons have, rare enemies that for all intents and purposes are almost as strong as a boss and share their immunity to stuns and other incapacitating effects. Their loot doesn't compensate for the trouble at all, and with a few exceptions they aren't relevant to any quest either.
 * In Dynasty Warriors: online, there are a few ways this comes into play, all of them more YMMV ways to think of them as mooks.
 * Players, when they set up correctly, and completely take you by surprise when you go in to attack, such as being able to murder your tanking setup in one hit, or having rendered themselves immune to flinching beforehand, meaning that when you attacked they could just turn and bring out the pain, or by using an item that allows them to change their move-set, but not their stats, allowing them to attack you in a way you didn't see coming.
 * If you have yet to face a general, the characters from the original games rather than a created character, you may be surprised on how much damage they can take, dish out, and they don't flinch, you are in for one short but harsh lesson. Aside from their battle aura, you may fully mistake them for another player, meaning that they seem so very mookish.
 * Star Wars: The Old Republic has three separate classifications of enemies tougher than standard-issue mooks: Strong, Elite, and Champion. Strong enemies are usually found alone, as opposed to packs of three for basic foes, and put up a significant fight. It's not uncommon for one to take out a player who made a particular blunder or aggroed one enemy too many. Elites are almost always isolated fights in open zones (in instanced Heroic and Flashpoint zones, which are meant for groups, Elites are the basic enemy), and are in many cases more difficult than actual bosses; indeed, most bosses are elite-grade. Champions exist for two reasons -- as a challenge for groups, or to obliterate players who wander into the opposite faction's territory.
 * Runescape has a skill called Dungeoneering in which the player travels through a cave called Daemonheim fighting monsters. Sometimes, it seems, that monsters and their levels are random, which means you'll find an ordinary looking mook who is severely overpowered. For example, a level 95 Giant Rat (who are usually level 2).

Platform Game

 * The Red Demon/Red Arremer from the Ghosts N Goblins series. It dodges your attacks with frustrating consistency, its dive attack is hard to dodge, and because of its HP, you have to dodge it a lot.
 * The obscure Platformer Scaler has Dragon War Beasts, enormous monsters with several attacks, they're only vulnerable after performing a certain attack, and gobs of health. They're usually only found at the end of Multi Mook Melees. However, there's also an extra-fast, camoflauging monster with high defense and HP that shows up all over the place - it's very annoying.
 * The Big Eyes (essentially 80's-style telephones on pogo sticks) from the original Mega Man. Sure, the game is Nintendo Hard, but these things are three times as tall and wide as Mega Man, take an immense number of hits to kill (20 buster shots), are immune to many of the boss weapons, and take off a third of Mega Man's health bar with one collision. Not to mention that they hop at Mega Man with impressive speed. The only way to get away from them is to run under them when they do an extra-big hop, which happens at random. It gets a bit easier when you get Ice Man's weapon, which freezes them in place for a few seconds, allowing you to either escape, or to switch to the P-Shooter and unload. Almost every Mega Man game since then had their own Boss in Mook Clothing, but none are as notorious (or stupid-looking) as the Big Eyes.
 * Ironically, the Warmup Boss added to the remake Mega Man Powered Up is the Proto Eye, a bigger yet laughably easier version of the Big Eyes.
 * ROM Hack Rock Man 4 Minus Infinity has the Jumbigs, which take 127 Mega Buster shots to kill.
 * The originally-named "Obsidian Enforcers" in Ratchet and Clank: Tools of Destruction. A few of them show up in the last few levels, and although their attacks aren't any harder to dodge than the normal enemies of their type, they have approximately 1.65 metric boatloads of Hit Points. It's entirely possible to empty the entire ammunition supply of a level 1 RYNO IV into one on Challenge Mode and have it survive. They don't get a health bar like the other type of miniboss, either, which brings up the truly horrifying thought that maybe they were just intended to be regular enemies.
 * Examples from the Metroid series:
 * The Black Space Pirates in Zero Mission. You can usually just run past them, but there are two you must defeat in the final escape sequence. Trouble is, they're much, much harder than regular pirates. Bad enough under normal conditions; tragic if you barely scraped past the final boss, which is likely in a low-percent or 100% run. These two bastards caused more retries and general frustration than anything else in the game until a good AI exploit was found.
 * To clarify, the reason players may be ailing after fighting the final boss at 100% is that the final boss's difficulty exists on a curve: if you're playing with 99% of items completion or less, the fight is one of the most absurdly one-sided Anticlimax Boss fights ever. But if you get 100% and then fight him, be prepared for a Nintendo Hard fight that takes glee in being That One Boss.
 * In several games, Ridley has a pair of souped-up pirates as his guards. They're no real threat in Fusion, but in Super Metroid, they'll trash you easily if you don't know what you're doing. It doesn't help that Ridley is That One Boss.
 * And let's not forget the metroids themselves. They don't look like much, but they're a lot more agile than most enemies, are resistant to many attacks, and do a lot of damage fast once they latch onto you.
 * The Fargul Hatcher from Metroid Prime 3: Corruption. It's in only one room in the game, and that's a good thing. It's only vulnerable while its mouth is opened- trouble is, it spews swarms of Fargul Wasps while doing this, and the wasps hunt you down. Meaning, 9 times out of 10, you'll be fighting the wasps more than the Hatcher. By the time the first swarm is dead, another will just be released. Last thing, the Hatcher itself has a ton of health.
 * Also, from the original Prime, the Baby Sheegoths, at least when you first encounter them. Can deal out huge amounts of damage, freeze you, take a serious beating, and are only vulnerable from behind. If you missed the Charge Beam earlier, you're going to break your thumb on the A button.
 * Grenchlers from Echoes are even worse. They do even nastier damage than the Baby Sheegoths, can jump up ledges, and their shells have rather wonky hit detection, making landing hits with the Dark Beam even harder than normal. Even worse, you have to fight a number of them underwater before you get the Gravity Boost.
 * Komato Annihilators from Iji. 4.7 metre tall death machines (good luck trying to jump over it), they have a large arsenal of weaponry, a melee attack thrice as powerful as any other enemy's, so much HP that they seem invincible, and an anti-knockback system preventing you from stunning them. They give a huge amount of ammo and nano if killed, but often not enough to make up for the ammo you spent killing them.
 * Yukabacera from the same game is literally one of these. He looks like an ordinary Tasen Soldier, but he is even faster than Iji herself (who is supposed to be the fastest moving person in the game, mind you), has plenty of HP (50 to be exact) and has weapons that could only be given to someone with a Tasen Stat of 10 and a Komato Stat of 10. (The highest level any stats can be) Kill him, however, and you'll not only obtain tons of ammo and nano, but the Scrambler as well.

Real Time Strategy

 * The Gatling Groink from Pikmin 2. It uses a powerful bombing attack with a wide blast radius, capable of killing many of your Pikmin in a single hit. It can fire a long way and usually has a wide "territory," meaning it's capable of reaching your Pikmin almost anywhere. Your captains can't really kill it on their own, and it has a shield that prevents it from being attacked from the front at all. To make matters worse, its health actually begins to regenerate once you "kill" it--so it'll just come back unless you have your Pikmin quickly take it back to your ship, which does it in for good.
 * The Adult Bulbear from the same game deserves mentioning as well. Unlike most enemies, the Bulbear will actively pursue your Pikmin once it runs into them. It will not stop until it is killed, and it can take quite a beating. Finally, it does the same health regeneration thing as the Gatling Groink, so you have to take it to the ship quickly, or you have to do the whole thing over again. Also, it's likely that you'll have to deal with Dwarf Bulbears along with the Adult, which will only increase Pikmin casualties. And in order to get 100% completion you have to, at one point, defeat 3 of them without any Pikmin dying.
 * The enemy placement in the underground levels is random every time you visit it, so the best way to defeat them is to just keep restarting until they spawn in a place that gives you a better strategic advantage.
 * The groinks appear in some multiplayer levels as well, which allows for an admittedly rather cheap but still legitimate strategy: particularly clever players can trick an enemy into leading their army past one of these.
 * In Starcraft: Brood War, during the final Terran mission, the Overmind deploys the "Torrasque", a souped-up version of the Ultralisk and a Shout-Out to Dungeons and Dragons' Tarrasque. It's an appropriate Shout-Out, for the Ultralisk is already a powerful unit, able to survive multiple Siege Tank shots and One-Hit Kill a normal marine: the Torrasque simply takes these traits Up to Eleven, allowing it to tank a Battlecruiser's Wave Motion Gun and still plow through even the most fortified positions. Worse, if it is killed, the Cerebrate in control of it simply respawns it a few minutes later. This makes it all the more satisfying when you can acquire your own Torrasque in one of the first Zerg missions and send him forth to single-handedly annihilate entire Terran bases. However, this one doesn't respawn if it dies, so take care not to let it take too many Siege Tank shots if you want to keep your super-Ultralisk.
 * Dawn of War II has Tyranid Carnifexes, enourmous, massively powerful creatures that will easily cleave through entire squads. There is one relatively early mission where the objective is the kill a Carnifex, and despite lacking any boss traits (special attacks and a health bar) it is just as difficult to kill. Attempting the Argus Gate mission-- in which three Carnifexes attack simultaneously-- without the Dreadnought is an exercise in futility.

Rhythm Game

 * The Rock Band games have these occasionally pop up in the forms of songs that are waaaayyy more difficult than their ranking indicates. The most infamous is probably the DLC song "Constant Motion", which is ranked at tier 5 out of 6, but contains what is probably the most difficult guitar solo of any song in the game (of which there are over 1000).
 * There's also "Can't Be Tamed" which most players will probably dismiss as a cakewalk at first glance due to only being a Tier 3 and being a pop song, but the solo section is so difficult that it should at least be a Tier-4 category.
 * Dance Dance Revolution Universe 3 had Conga by Miami Sound Machine as a boss song, and the first license boss song in DDR. It's Oni chart is one of the most clustered charts in the series, that playing without a speedmod is suicidal.

Roguelike

 * Of the many, many unique monsters in the Roguelike game Angband, only Sauron and Morgoth are mandatory Boss Battles, and even they don't appear in specific Boss Rooms on the levels they guard.
 * More standard examples of bosses in mooks' clothing include the Drolem (one of the earliest max-damage poison-breathers, and one reason you don't go past 2000 feet without poison resistance; also drops a pathetically small amount of treasure), the Greater Titan (summoning, lots of HP, high-damage melee attack), and the Great Wyrm of Power (as the description says, "it can crush stars with its might").
 * Though a staple in most rogue-likes, Elona has a particularly nasty variety of them. Adamantium Golems are green golems with incredible power, defense, health, and damage-adding abilities. Note that up until this point, golems merely advance in power consistently. Don't mistake them for being this game's Incredible Hulk, however, they are actually his much more indestructible rival/ally Wolverine. By the time you land a second critical hit, which seems the only thing that will actually kill them, they may've healed up the damage from the first. In the lower levels, mutants qualify, as mutants spawn with A) a random amount of limbs, and B) totally random equipment, 30% of the time it is magical in nature. Woe to the player who discovers a three-armed mutant with an enhanced weapon and shield. Both of these are encountered more rarely than other random monster spawns at the same level. If in a dungeon whose levels randomly generate, the best course of action to deal with an adamantium golem is to zap it with a rod of teleport, then flee up or down the stairs and come back. Note that for the truly unlucky, any enemy in the game may spawn as a random dungeon's "last floor boss," making the Addies more terrifying still. See also quicklings, simply replace the abundance of defense with speed.
 * There is also the Shub-Niggurath, a rare spawn at about level 25+, who is pretty tough to kill. Luckily, they are only half-assed hostile, prefering to summon other creatures to do their bidding or hit you with mind-screw sanity-altering affects, as their name would imply. They only directly attack you if you engage them in melee combat. Their biggest danger comes from the randomness of their summons, as they may summon something that will mop the floor with you, even if you're to the point you can one-shot a Shubby. Like the golem mentioned prior. Still, that's an incomprehensibly rare occurence. More often than not they may even summon neutral or friendly NPCs who will help you fight them off. It's all chance when dealing with these, really.
 * The Roguelike game Ancient Domains of Mystery has a number of these that, while rare, are extremely deadly. Emperor liches are a good example; they are powerful spellcasters and can damage the player's stats, summon numerous monsters and cast Death Ray. Diamond Golems absorb every element and have very high defense. Molochs will ruin primarily melee characters or characters with very low speed. Greater titans absorb every element, too, and shoot eternium quarrels (which hit hard) from a distance. Great Karmic Wyrms cast spells, are also immune to all elements, and hitting them makes the player unluckier with each hit.
 * Parodied in this page, which describes a Ninja Pirate Zombie Robot monster with an Overly Long Name and all of the most notorious abilities of various monsters in the game.

Role Playing Game

 * One of the earliest and most notorious offenders is the WarMECH (later translated as "Death Machine", then back to WarMECH) from the first Final Fantasy game. He has as many hit points as the penultimate boss, and his attacks range from powerful regular attacks to literally nuking the party on the spot. There is also the distinct possibility that you can run into TWO WarMECHs at the same time, which is pretty much a death sentence.
 * The Updated Rerelease version was actually made worse - they doubled its hitpoints and it regenerates 100 hit points per round (due to its high defenses, even knocking off 100 hit points per round is something you won't do until much later than your first potential encounter with it). In the both the original and the rerelease, people find it more difficult than the Final Boss. But you only have a 1/64 chance of encountering it, thus making it a Bonus Boss in Mook Clothing.
 * The Earthgift Shrine bonus dungeon has Abyss Worms. Higher Attack than the four bosses (and the four Fiends!), no magic weakness, and such a high M Def as to make your Mages practically useless. Good luck.
 * The Brachioraidos is a recurring one in the series. Its looks and translated name have changed drastically with each installment, making it hard to notice. Its appearances in order have been:
 * Final Fantasy VI as the Brachosaur. Based on the brachiosaurus. It casts Ultima.
 * Final Fantasy VII as the Vlakorados. Square stops caring what the monster is shaped like.
 * Final Fantasy X as the Th'uban. This one breaks the tradition by being a bonus boss.
 * Final Fantasy IV Advance as the Brachioraidos. Not a random encounter but a roaming sprite.
 * More examples from the Final Fantasy games:
 * Later Final Fantasy games usually have Behemoth in this role. This could also be considered a meta-example the Degraded Boss, as Behemoth debuted as a boss in Final Fantasy II, but is a recurring ultra-strong "regular" enemy in the rest of the series. Final Fantasy IX had a monster called the Grand Dragon in a certain place accessible around Disc 1 that exists for the specific purpose of screwing you over if you don't heed the nearby Moogle's warning. Adequate preparation (stock up on Phoenix Downs, equip everyone with Antibody and Auto-Reflect) can render these Grand Dragons quite beatable, and thus turn this early accessible area into a convenient high-speed level-up treadmill. (Doubly so if you realize the Grand Dragons are a multiple of level 5, and it's quite possible to have Lvl5 Death by then.)
 * The Jackanapes from Final Fantasy V (known as "Harpy" in the PSX version) is an example of one of these. The first time you can encounter it, its attacks will do several hundred more points of damage than you can take(even at higher levels, it will still eat your HP quickly), and it's fast enough that you're almost certain to lose one or two party members before you can run away. Oh, and it can also dodge almost ALL of your attacks and magic, so if-- no, when-- you are unlucky enough to meet one, you won't be able to fight it out.
 * Final Fantasy V has a few "super" enemies like this. There's the above mentioned Jackanapes and Skull Eater, but also the Prototype (which has a couple of glaring weaknesses, but is very hard to hurt otherwise), the D.Chimera and a group of five Mini-Dragons. Also, at a later point in the game a moogle advises you to avoid a desert; heeding such advice awards you an enemy-free journey, but disregarding it sends you against another set of very powerful mooks. Super enemies in this game are usually characterized by exceptionally high defensive stats, forcing you to rely on otherwise unorthodox strategies.
 * The Tot Aevis from Final Fantasy V Final Fantasy V's Merged World brings this trope to mind. The enemy itself appears in a plot related, but ultimately optional dungeon. While most enemies have between 2 to 4 Thousand HP, rendering them kill-able in a short time, the Tot Aevis has 33,000 HP, more than the boss of the dungeon that contains it. It can make use of a Wind Attack that targets all of the party, and has a single target attack which can inflict Petrify. The reward when killing it is 7ABP, more than the multiple enemy formations in the dungeon, second only to the boss, but otherwise gives nothing else, no EXP, Items, or Gil.
 * Yans from Final Fantasy IX. Cute little lambs that proceed to Comet and Meteor you to death. Thankfully, they're only found in one optional area. Unfortunately, if you want to be able to melee Ozma, you're going to have to go there to get the last friendly monster encounter (who also happens to be a Yan), making the risk is necessary. Since Ozma is the simplest source of the pumice...
 * FFIX also has the Zombie Dragons first found in the Iifa Tree. While not too hard to defeat in retrospect (especially considering Revive Kills Zombie), these guys are the first enemies in the game to hit you with LV 5 Death, which they like to use on their first turn. And of course, when you first enter the Tree, most if not all of your characters are level 30 or so, which means encountering one of these bastards is a Game Over unless Lady Luck decides to intercede on your behalf.
 * There's several from Final Fantasy VI. A Tyrannosaur has 12,770 hitpoints and can cast Meteor. Mantodea's other stats aren't anything special, but its regular old attack can wipe out most characters in a single hit.
 * There's also the Fiend Dragon, found in the final dungeon. It's rare, but if you run into it, you have to deal with a monster that not only packs high HP and powerful magic, but also is the only monster in the game to have Heartless Angel, which reduces everyone's HP to 1. It then likes to follow up with South Cross, which also hits everybody, and will probably wipe out the whole party. Isn't that fun?
 * And then, there's the Intangir on Triangle Island in the World of Balance. It has auto-Vanish, a staggering 32,000 HP, absorbs all elements, and is immune to almost every status effect. Most of the time, it doesn't do anything, but if you try to get the Vanish off it so you can actually hit it, it'll smack your party with Meteor and disappear again. The only legitimate way to beat it is to cast Stop on it, beat on it, heal yourself after Stop wears off, and repeat as necessary. When you finally bring him down, he will hit whoever killed him with Meteor, which is a guaranteed kill if it connects. You gain no experience for beating him, but you do get a whopping 10 Magic Points.
 * The Vanish/Doom trick works well against the Intangir since it's already invisible, though it will still hit whoever casted Doom with Meteor.
 * Final Fantasy VII: The Unknowns in the Gelnika probably qualify, as do the Ghost Ships in the Junon Reactor (which know an attack which removes a member of your party from the battle, and have to be morphed into items to stand a chance against one of the Bonus Bosses without using any exploits). It also had the notorious Midgar Zolom. It's tough to find unless you know where to look, and it uses an attack (Beta) that will nuke your party (literally), as well as normally potent attacks. The silver lining? Enemy Skill Materia can make Beta your Disc One Nuke (if you survive it, assuming you survived long enough for him to cast it).
 * Final Fantasy XII had a whole slew of these called Rare Monsters. They showed up among the normal fights on the world map, but were boss-tough. Generally, though, they only came after you if you attacked them first.
 * There's also Wild Saurian (which shows up in the first open area of the game), the Werewolf (second area this time), Dive Talon (shows up early, but you can get a Disc One Nuke from it), and the Entites.
 * Also, the Wild Saurian eats the wolves in the area which adds to its overall HP and actually allows it to level up.
 * The Elementals can count since they're usually of a much higher level then the players in areas they are found in, and will aggressively attack the player if they so much as whiffed even a scent of magic in their area. Even White Magic will cause them to go Aggro. They also are immune to all elements, except their own, which they of course absorb. They also take around 1/2 damage from physical attacks.
 * Final Fantasy VIII has T-Rexaur. The game even tells you that "It's better to run if you encounter one".
 * There are a handful including Elnoyles and Ruby Dragons which both have strong attacks and very high HP.
 * It's better to run from every single random encounter, but that's neither here nor there.
 * One word: Tonberries. Loads of HP, and two signature attacks. Knife a deadly stabbing attack which the tonberry must usually spend time getting into range to use andEveryone's Grudge (aka Karma), which is based on the amount of enemies (or sometimes tonberries) that the target has defeated. If you're finding yourself in a place chock full of Tonberries, switching to a party that hasn't been used much can help.
 * Oddly enough, the Tonberries in Final Fantasy VI (which were called Pugs in the original US translation) were much easier. You still had to have a fairly high level to beat them, but you were already close by the time you got to that part of the game anyway. However, they also punish you for level grinding, in that their main spell (which Strago can learn) is Step Mine. It does damage based on how many steps you've taken.
 * Everyone's Grudge in Final Fantasy XI is based on the amount of Tonberries killed, and only them. Since you can't exactly switch out for another character solo, there's a quest in the game that allows you to reset the "Tonberry Hate". You'll need it, as some Bonus Boss Tonberries can use Everyone's Rancor, which hits for 50 HP for every Tonberry killed. While Everyone's Grudge can be annoying most of the time, not resetting hate before facing a Tonberry with Rancor any time is suicidal.
 * Uragnites in Final Fantasy XI hide in their shell the second you hit them, which has them acquire massive damage reduction and a powerful Healing Factor effect, and any further physical hits while in the shell will be countered with a deadly area poison effect. It's normally best to build TP and use a Weaponskill when the thing pops out again, while mages can just whack the shell once, then run away and nuke safely while it's in the shell, immobile. Even being level 75, one of these mobs at 30-ish take awhile to kill.
 * Malboros have a lot of HP, and can inflict so many status ailments with one move that an unprepared party can wind up killing each other instead, if they aren't outright defeated by something like Petrify or an Instant Death countdown.
 * Don't forget Great Malboros in Final Fantasy X, particularly in the Omega Ruins. All encounters with Great Malboros in the Omega Ruins will be "Ambushed!" encounters; if you don't have First Strike in any of your characters' equipment, prepare to face anything from a mere normal attack to the dreaded Bad Breath, which will most likely inflict Confusion on your party members, causing them to kill each other and themselves.
 * Final Fantasy X has a lot of these enemies. In the final dungeon, about half of the enemies have either powerful party-hitting attacks, a lot of status immunities, the ability to inflict tons of bad status effects, or some combination of the above. And they all have over 40,000 HP.
 * In some cases, Cactuars can be a pain. They typically have the maximum evasion rate and throw 1000 needles at your party. Then they have the nerve to run away. But if you defeat one, you're usually well rewarded.
 * Some Cactuars in the games, especially the ones in FFX are even worse than the regular ones. Quactuar for the weaker, 1000 needles at one of your party. Then the Cactuar for the actual pain in the arse. The Cactuars in FFX will do a 10,000 needle attack that leaves one of your characters dead unless you broke the HP limit with a customized armor, which is nearly impossible to do as you will be facing one before you can get the items required...
 * And then there are the ones in the Monster Arena that use 99,999 Needles...
 * Oddly enough, this is kind of averted in FFX when you use items that damage on them. Their maximum evasion goes on strike and you hit them all the time. This is probably why Rikku was placed in the game, her "use" ability allows you to single-handedly take these annoying little suckers down fast.
 * Final Fantasy III has the Yellow Dragons. Harder than most bosses, but they can drop Onion equipment.
 * There are also green and red dragons. Both are stronger. The only thing stronger than red dragons is the final boss, and the Bonus boss added into the DS version.
 * Final Fantasy IV for the DS in general has a lot of these, adding to the already Nintendo Hard nature of the game.
 * You may encounter a variety of dragons after you recruit Edge that possess a lot of HP and may have a nasty attack. One of the worst is the Thunder Dragon, which is slightly faster than your characters and uses a powerful attack. Good luck trying to revive your tank.
 * There will be instances where an enemy will have a party-hitting spell (whether it'd be a normal spell or a special attack). At first these aren't too dangerous, but then it gets ridiculous to the point where two of these can kill a party that's overleveled. Oh, and they love to come in groups.
 * Trap Doors in the Sealed Cave. They cast instant death spells that are 100% guaranteed. But they have a weakness: reflect their death spell back at them!...which you can't do without Augments thanks to how their spell works. If you're not playing the DS version, good frigging luck.
 * Everything in the final dungeon. The last two floors are also applicable to the original version. The really fun part? A lot of enemies in the final dungeon actually have the boss music playing during their fights. Lampshade Hanging?
 * Right near the beginning of the game, Sand Worms. Which you can encounter between Mist and Kaipo. At a time when Cecil's your only party member. Sandworms can take about ten hits from Cecil at this point in the game, and can deal 200 damage to him when he'd only have 300 HP.
 * What makes this particular encounter worse is the fact Sand Worms are fairly easy in the original versions that you're likely used to by now, and you may not have realized yet how much harder the DS version is. You will when that Sand Worm completely annihilates you.
 * If you're a ways into a Final Fantasy game and you find a one-eyed floating bat thing, run. While their names are never really consistent (Ahriman, Doom-Eye, Blood Eye, etc), they have one thing in common, they have instant death attacks. Thanks to the computer being a cheating bastard, the useless useful spell rule usually doesn't apply. This includes straight up instant death, a form of Russian roulette (never lands on the caster for some reason), and some form of death countdown attack. There is a trick for taking them down safely in FFIX, though. If you do nothing before they use their Roulette attack, it will end up targetting themselves.
 * Final Fantasy X-2 has Azhi Dahaka, which guards the electric gates that block the way to Vegnagun at the end of the game. Screw up on one note, get frustrated with the entire puzzle, and then try to go through the barrier thingy anyway? Yeah, bad idea. Only good thing about that monster is you can run away from it.
 * A lesser example is Aeshma in the prior area. It has relatively high HP for that area, made all the more noticeable by its unbreakable barrier that prevents all physical damage, meaning no critical health Cat-Nip'd Trigger Happy gunner can save you. And while you CAN escape, it won`t help if it hits you with Emblem of Thanatos, which does boss-level damage (well over 1,000) and is the first sign that it's more trouble than it's worth as it appears as a normal enemy.
 * Starting with Chapter 11, Final Fantasy XIII has a bunch. Ochus, Tyrants, and Juggernaughts all fit the bill well enough, but the absolute perfect examples are the Adamantoise and relatives. Attacking one as soon as you get to Chapter 11 is guaranteed death. No real room for tricks there. Thankfully, they're quite docile and easy enough to avoid.
 * Another example from XIII is the King Behemoth. They're rather common in Pulse, often seen prowling around and sometimes fighting other enemies. What makes them so hard? They have a TON of hp, and they also take quite a while to stagger. Get him down to half health, and he instantly heals up to full health and stands on his hind legs. He's even harder to stagger now, and does a brutal physical attack that will kill anyone but a guarding Sentinel, as well as casting an Area of Effect lightning effect that will probably kill your Medic or Ravager. He's possible to kill in Chapter 11, but only barely, and you need a lot of patience.
 * Ishtar from the Final Chapter of Live a Live can be described as a random encounter miniboss.
 * Live a Live also has one in the Prehistoric Chapter and one in the Bakematsu Chapter. They warn you by using the boss music when you encounter them, though- and there's a rather small chance that you'd run into them without knowing.
 * Abyss Bat in Saga Frontier; granted that you have to wait around for him to show up, but he puts up quite a fight.
 * The Wild Arms series has many of these, which are usually farmed for experience points or rare items. The most infamous are the Hayonkonton/Hyulkonton/Creeping Chaos, but there are others like the the Apeman Vargon and Jumbo Bearcat.
 * The Amazee Dayzee in both Paper Mario and Paper Mario: The Thousand-Year Door wholly crosses over with Metal Slime. It might just look like a sparkling Crazee Dayzee, but it has 20 HP (most of any mook in the first game, and tied for second-most in the second game, behind the Dark Koopatrol), 20 Attack, 1 Defense (in a game where any sort of defense score is notable), and their attack can also cause sleep. It also has an attack that has unintuitive timing to defend against, and definitely needs a lot of strategy to beat...because, due to its Metal Slime nature, it's likely to run away first chance it gets. Especially in The Thousand-Year Door, where if you actually encounter one on the map (completely by chance) the first time you go through that area, 20 damage will be almost enough to kill you from full HP. And then on the return trip from said first journey, and have to pray that it will run. More than capable of murdering any unsuspecting player.
 * Thousand Year Door provides a decent way to beat them once you get the Ruby Star and gain Art Attack. By concentrating loops around the Amazee Daisy, you can hit it for enough Armor-Piercing Attack damage to beat it (or at least leave it just one good hit away).
 * The first Paper Mario features the four Anti Guys. Take regular mooks, give them 12 attack (where par is 2 or so and your HP limit is 50, though you're more likely to have 30 or so) and maybe twice that in HP. Oh, and in the second fight you fight three at once. At least none of the fights are mandatory.
 * However, if you can beat the Anti-Guys, it makes Bowser feel like an Anticlimax Boss.
 * The Spunia looks a lot like Spinias and Spanias with some spikes on top...until you check its stats.
 * A lone Elite Wizzerd in The Thousand-Year Door probably isn't tough enough to count (despite having both the "needs a lot of strategy to defeat", to some degree, and the "has a variety of different attacks" qualifications). Unfortunately, they generally come in groups of four or five. A defense of 5 is almost insurmountable in this game, so you pretty much need to use defense-ignoring attacks (here's hoping you've got plenty of Star Power--Art Attack works well, but even from a full meter, you can only chain two of these). They have 12 HP each and have three different damaging attacks, one of which does 8 damage to one party member and one of which does 7 damage to both party members. They can also buff their attack or defense, become dodgy (attacks may miss), become transparent (attacks will miss), electrify themselves (deal damage if you try to attack them directly), heal themselves, and when only one remains, it will inevitably split into five, only one of which will actually take damage. And they only appear on the lowest levels of the Pit of 100 Trials, after you've likely worn out your items and star power fighting Piranha Plants and Dark Bristles on the previous stage and regular Wizzerds on the stage before that.
 * Super Paper Mario features an enemy called Mega Muth, a white mammoth like creature found in Castle Bleck. Numerically stronger than the final boss, you have to fight a whole corridor full of these things. Luckily, they're slow and can easily be dealt with by throwing them at each other. But there's an even stronger subspecies in Flopside's Pit of 100 Trials...
 * The Archmage and the Berserker, enemies in the Container Yard of Breath of Fire 3 are actually tougher than the final boss. The Archmage even has a skill that revives your entire party. Why? So he can kill you again.
 * Similarly, the Rider enemy in Breath of Fire 4 is much stronger than the final boss, using the game's strongest spells on the party, and healing itself an absurd amount every turn.
 * Breath of Fire 2 already contributed the K. Sludge and the N. Rider to this trope. The former came in groups of three and packed a very effective Instant Death spell, and the latter can use all of the highest level spells in the game.
 * Suikoden occasionally likes to toss high-level monsters onto the overworld map just to mix things up. This is usually accompanied by a change in battle music.
 * Dungeon Siege has this to some degree: occasionally you'll see enemies lit by a Pillar of Light, with the same attack power but usually 3 times more HP than your average foe. The third game does away with the pretense and gives them the same onscreen health meters as normal bosses.
 * Etrian Odyssey, being a Nintendo Hard dungeon crawler, has a ton of these monsters, designated as "FOEs" (shorthand for Fucking Overpowered Enemies) in game terms. First appearing on the second level, they appear as arrows on your map, and most of them look exactly like the normal enemies in the dungeon...but have vastly higher HP and attack power. Some follow set movement patterns, while others will rush your party when you get in their line of sight. Others, once they sense blood (such as the Wolves and Skolls) will actually join other FOEs mid-fight to make your life even more of a living hell.
 * Even on TVTropes, F.O.E.!
 * The sequel, Heroes of Lagaard, in addition to having a F.O.E on the first floor, takes this one step further. A specific random encounter has 10,000 hit points, more than five times the number of hit points of the next strongest random encounter, and 3000 more than the strongest FOE the game has to offer. Said random encounter also has a multihit attack on your entire party what will usually OHKO any of the non-tank classes, as well as a skill that prevents you from using any of YOUR skills. Said random encounter also holds the dubious distinction of being the only FOE or random encounter in the game that is immune to Instadeath Skills (most Bosses are immune), and the ONLY enemy in the ENTIRE game that is immune to Stun. 'Boss in Mook Clothing', indeed.
 * Wanna get your ass kicked in the Bonus Dungeon of Valkyrie Profile? Right before the final Bonus Boss, there's usually a normal battle Palette Swap of an normal end game boss. Tough, but doable. However, there is a small chance that you will fight hamsters instead. Normal looking, regular sized hamsters. Prepare to die.
 * The elephants in The World Ends With You. They spam an annoying attack - a stomp creating a slowly widening shockwave - that can interrupt any attack. Easy enough for Neku to dodge, but you might have to actually start paying attention to the top screen so your partner doesn't end up making you die. Even if you're using the partner that can float in mid-air! The damn ground stomp knocks him out of the air!
 * And then they supercharge one and set it as that one Bonus Boss.
 * Too many enemies to name in the Shin Megami Tensei series - fortunately, most of them have a Outside-The-Box way to defeat them, in an aversion of Useless Useful Spell. Most.
 * Hell, it's practically a given that the random mooks in the last (and possibly next-to-last) dungeon in all Megaten games will all, without exception, be totally immune to every kind of attack save one. Don't have that damage type/status effect in your group? Why, I believe it sucks to be you right now. Have it, but the character is out of mana after running into one of them too many? Oh, but your tears of frustration are just yummy, my dear.
 * An Egregious example would be the rainbow-colored Maya in The Answer (Persona 3). It has high resistance to damn near everything except Almighty attacks plus can nuke pretty much any party member with Black Viper (single target Almighty spell). Woe unto you if it hits Aigis.
 * The Avenger Knight, also from The Answer, will teach you not to mess with the tiny, red Shadows. Insanely high HP, blocks light and bounces back dark, reflects Aigis' physical attacks, and has no weakness. It also hits like a truck with strong Zio (electric) and Slash attacks.
 * There is a particularly annoying team in Devil Survivor. The Leader: Some Magic-prominent reviver/healer. The other two? Berserkers. Who always have Endure as their one of their abilities, which allows them to always survive an attack with 1 HP left. Needless to say, it's almost impossible to take down even one Berserker AND kill said leader before one is revived, and the leader gains almost perfect defense again.
 * There's also the Decarabia. Offensively, they're decently strong with their fire spells, but nothing special. Defensively, on the other hand...they have Shield All which they abuse often, and have Sacrifice, giving them health at the end of every turn. Pair them up with two strong fighters, like Berserkers (mentioned above), and you have a group of monsters that are difficult to hit, deal high damage, and will end the fight with full health.
 * There is a complete reversal of this is in Digital Devil Saga. The final secret boss is the from Nocturne. His random encounter music plays during the battle, giving the impression that you're just a random bunch of mooks for him. And quite frankly, if you're not prepared, you are.
 * Strange Journey has a system of special battles in which you use a special visor to find rare demons and battle them. Most of the encounters found this way are quite strong, but drop valuable remains which can either be sold for a lot of money or used in high-end weaponry. However, every now and then, horrifically overpowered demons pop up. The finest examples are the Fiends, but there are plenty of others who occasionally come up with a hankering for your guts.
 * Wizardry VI: Bane of the Cosmic Forge, from a series known for random encounters sometimes being tougher than bosses, has a very, very low chance of the party encountering a Tyrannosaurus Rex in the final outdoor area of the game. It's unlikely you'll see one in six or seven games, but if you are that unlucky, it is game over. Nobody has ever successfully taken down a Tyrannosaur.
 * Mother 3 - One word: Cattlesnake. It has more than twice as much HP as any other enemy in the area, and has a ridiculously high defense - characters that do 50 damage to other enemies will only do 10 damage to the cattlesnake. It also has an attack that can hit the whole party for 70-80 HP damage per strike - at a time when your characters will average about 140 HP. Before you first see one there is a sign warning you to keep your distance.
 * On the subject of Earthbound: Final Starman. Capable of spamming PSI Starstorm Omega (!!!), Brainshock Omega (confuses everyone in the party), and Healing Omega (fully revives any defeated enemy). Oh, and they start out with maximum shields, which completely deflect PSI attacks and bounce physical attacks back at you. Couple that with the fact that they usually appear with Ghosts of Starmen (see Demonic Spiders) and Nuclear Reactor Robots (spends its turns healing enemies to full health AND explode when you kill them)...can you say Total Party Kill?
 * The Nintendo Hard RPG The 7th Saga has a variant: every random encounter is like this. The bosses themselves are often significantly less likely to kill you than the random encounters in the dungeon that contains the boss.
 * The Sootie family in Star Ocean: Till the End of Time's Bonus Dungeon Sphere 211. A single one can easily kill a level 255 party (which is downright absurd, considering the fact that the game's uber-Bonus Boss Freya can't even damage characters that the normal enemy Sootie Sister could kill in one or two blows), and they are a pain in the ass to even hit. Demonic Spiders much?
 * Star Ocean 2: The Second Story has this pretty much at many points of the game. In many dungeons there will be enemies that will instantly petrify your party, and will require constant stunning to prevent the group-petrifying attack. Attacking so often the enemy can't do anything is a major tactic for most enemies. In the bonus dungeon, most of your characters will have a Star Guard, equipment that upon a successful block, will do an attack which releases multiple attacks that can do 9999 damage a piece, and even then, you will die if not careful.
 * The Might and Magic series had this whenever you face a spellcaster. If it could cast certain spells, you were simply doomed. Namely, Meteor Shower (with which you could often kill your OWN PARTY with) and Shrapnel are two of the most deadly, and sometimes Death Blossom could also put you in a world of hurt.
 * Don't forget Finger of Death which was a one hit kill, or Eradicate which literally destroyed one of your parties bodies so that they could not be brought back to life with the Raise Dead skill. You needed an even more powerful Resurrection spell to heal them.
 * Or Dragon Breath from MM7.
 * Wyverns in The Witcher also qualify to this, as they're very tough and when you encounter them, even on the Easy level, they're hard to kill. Especially as they always come in packs of about 8.
 * Let's not forget that they can drop right out of the sky, so when you think you're approaching one or two manageable enemies, you can suddenly find yourself surrounded, poisoned, knocked down and/or pained.
 * The standard Wyverns are lion-sized yellow-orange looking bastards that can be taken down relatively quickly if you know what you're doing. The royal Wyverns you encounter later are twice the size of regular Wyverns and can kill you in a few hits with their poison! Be damn sure you drink a poison resistance potion and equip a silver sword smeared with ornithosaur oil before you take them on.
 * In the final dungeon of Phantasy Star IV, you may run into a Prophallus, uber-monsters that bear a striking resemblance to the final boss of the original game.
 * Phantasy Star II had Blasters in the Bio Lab and Nido Tower areas. If you met one, your best bet was to either run or nuke it with every single bit of firepower you had. Meet two? Pray you can run, OR ELSE.
 * In Phantasy Star IV, the first Sand Worm you fight (usually) is a boss. However, when you get your first vehicle and cross the sand pits, you'll encounter them as regular mooks. That first sandworm is that it's an extremely difficult boss fight when you first get to where you can take the mission for it, often capable of killing or at least severely wounding a party member per round, before you have access to resurrection items-- and that one doesn't have all the regular Sand Worm attacks. It can't use Earthquake, which will destroy an un-buffed party even twenty levels later. The kicker is that one of the types of little worms you fight in Motavia will run off and summon another full-powered Sandworm if you even leave one of them alive. Surprisingly though, Sandworms do provide a hefty amount of Experience points, despite their difficulty, if you pull off the right combinations you can just set a Macro based off of that turn to toast it every time.
 * It's a good thing Avernum 5 only does a mild version of this, because it gets used constantly.
 * The Game Boy RPG Robopon has - erm, well, quite a lot of them. Perhaps the worst offenders, though, are Move-type Robopon. They use attacks that increase their speed to insane levels, making it almost impossible to land hits on them. To make matters worse, they generally have either high Attack or Defense, meaning they'll either pulverize your team into the ground in seconds or take what hits you do land on them and shrug it off like it's nothing. To make matters more insulting, when you use Move-types, they often end up gimped because The Computer Is a Cheating Bastard and has access to better moves and equipment than you do.
 * Some of the enemy monsters in Monster Rancher have a tendency to be much more powerful than other monsters, even of their rank--and it's not just the ones intended to be stronger, like those used for invitation matches. Enemy Gaboos in Monster Rancher 2 tend to have ridiculously powerful moves, as do Golems--in any game.
 * Fallout 3: Deathclaws are exceedingly ferocious and can demolish even high-level players if they are caught unawares. Super Mutant Behemoths are considered the "bosses" of the game, as there is an achievement for killing them all, but players have proven that a Deathclaw can kill one in 1v1 combat.
 * While not quite as lethal, the Mirelurk Hunters and Giant Radscorpions deserve honorable mention. They are much stronger than their weaker variants, come out of nowehere once you hit a certain level, will kill you if you haven't been upgrading your combat skills, and the Mirelurks take very little damage unless you Attack Its Weak Point.
 * Those are all actually extremely easy with the proper use of landmines, which you should have by the time you encounter them.
 * Also with an easy-to-get and easy-to-get-early Lincoln's Repeater with some Sm Guns skill and VATS-aiming at the face.
 * The Yao-Guai, when first encountered, can be like this due to its ludicrous speed and raw, unstoppable power. Your only hope before you can easily kill them through over-leveling is to catch them as far from you as you can and shoot them in the head as many times as possible before they close the gap between you and them. Due to being able to run into them before finding the shotgun, they can be horribly brutal, nearly impossible to kite, and sometimes come in pairs. They're also quite capable of taking a full mini-gun burst if you aren't skilled enough.
 * Yao Guai and Deathclaws are the single biggest reasons to find and craft a Dart Gun as quickly as possible. The weapon cripples the legs of anything it hits, and a Yao Guai or Deathclaw with crippled limbs, in addition to being a great deal slower, also cannot lunge.
 * The Broken Steel expansion DLC adds Super Mutant Overlords, Feral Ghoul Reavers, and Albino Radscorpions. All 3 enemies have incredibly high boss-level health and massively damaging attacks. Even high level characters can find that an entire VATS cycle of high-end attacks that can kill all other enemies in just a few hits will barely scratch their health meter.
 * The Overlords and Albino Radscorpions are at least used like bosses, in that you almost never fight more than 1 than a time (2 at once in certain very specific situations). However, there are multiple free-roam dungeons and one main plotline mission near the end of the game where you're expected to fight several Feral Ghoul Reavers at the same time. Bear in mind each individual Reaver is about 1/2th as tough as a Behemoth, and hits almost as hard.
 * Speaking of DLCs, Point Lookout had the Swampfolk. They look like normal (if slightly deformed and deranged) people, yet their attacks hit for much more than you would suspect. This is because they, like Deathclaws, have the ability to ignore your damage resistance. But unlike Deathclaws, they do not have sharp claws or other special abilities. The developers have said that they made the Swampfolk so strong because they wanted Point Lookout to be the hardest DLC and also because they wanted to create the "Lovecraftian" feeling of having to run and hide from mysterious enemies; instead of just running in and slaughter everyone with your minigun.
 * The original Fallout had a single Deathclaw as an incredibly rare random encounter while traveling on the over world map; considering most of these random encounters are generally more of an annoyance than a challenge after awhile, any person playing Fallout for the first time was in for a slaughtering.
 * In Fallout: New Vegas, the game introduces a new enemy type known as the Cazador, which although very small and having the appearance of a much weaker enemy, the Bloatfly, can decimate low level players with its poison within a couple of hits and as nimble. Not to mention, they come in packs of up to five. They are often used to wall the low level player in, forcing them to take a specific route in order to level up first.
 * These are so common in Mana Khemia Alchemists of Al Revis that they actually get their own battle theme and a special icon in the game's Preexisting Encounters system. Early examples include the Bear, Owl Bear, Sword Geist and Shield Geist. You also get twice the normal AP for winning a battle containing one or more of them, so they can be worth the risk. Yes, the game gives this much fanfare to regular enemies that are much harder than the norm. Appropriately, actual bosses, by comparison, have a downright epic battle theme and look about as intimidating on the map as a red blob can.
 * In Wizardry V, there is an optional level. If you go down there, the enemy strength widely varies. You might get some ghosts, which do almost no damage and have very low HP...or you might get enemies like Dark Lords and Arch Fiends who have several times more HP than even the end game boss and spam the best magic in the game, including a spell that can kill your entire party at once if you're unlucky and another spell that does around 100 damage to everyone when triple digit HP is a big deal and healing is hard. They might attack you normally instead, in which case the target, if not killed by raw damage is probably instant killed anyways, and drained about 5 levels. They also spawn with lesser (but still powerful) demons, who throw in more firepower. Worst part is while you aren't technically required to go down there, it's the only way to get the best equipment in the game, which among other things gives you the magic resistance you need to not die in 1-2 rounds against...nearly any late game enemy. Especially the aforementioned end game boss. To be fair though, it does play the boss music to warn you...but it's still a random encounter, and you might not be able to escape.
 * Slivers in Tales of Symphonia, a slightly less powerful version of the Sand Worm (also technically not a boss, but not encountered randomly and guarding one of the Devil Arms). They appear very rarely in the snow fields near Flanoir. Very, very rarely. Will probably be the last monster you need to complete your Monster Guide.
 * The second (optional) Card Key in the Iselia Human Ranch in the sequel is guarded by a group of tiny leeches...with ridiculous amounts of HP that they constantly heal, and that deal a ton of damage. If you don't have very strong Mons with you, you are certain to get party wiped unless you use the run command. If you do have very strong Mons with you, you are almost certain to get party wiped.
 * The Bahamutt enemy in Super Mario RPG straddles the line between this and Sub Boss, as it is only encountered when summoned by Chester or Magikoopa (a Chest Monster and Boss, respectively). It has a unique sprite, packs stats that are stronger than most bosses fought in the final area and is one of two non-boss enemies to have over 1000 HP. Also, it has an attack that causes Fear, halving a character's Attack and Defense.
 * Dactyls in Titan Quest only look a little different than other mooks in the dungeon where you find them, but they will paint the floor with your innards if you aren't expecting anything different. Then they'll do it again if you were expecting something different.
 * Persona 4 sometimes features random encounters ten levels above the norm for the particular dungeon they may be found in. These enemies will generally be able to kill anyone in your party in a single hit - and sometimes all of them in a single attack. Even then, there are encounters in which you'll be up against three or more enemies your own level who all cast high-probability instant party kill spells every turn. Three guesses who developed and published the game.
 * Despite the fact that it's relatively forgiving for an Atlus game, if the AI lines up just right then a normal encounter you've blown through 20 of in that dungeon will suddenly become frighteningly competent and cause a near total party wipe, even on easy.
 * In Eternal Ring there is a secret area Inside are rats that are easily one-shotted, floaty orbs that die in three pokes of a sword, but go on a (long) self destruct timer, and the werewolves. They take several castings of the weapon or dragon summoning spells (dragon spells are as big as it gets here), they take more than half my HP even now with their attacks, and I'm approaching the final boss after grinding about 10 levels in this secret map! There are giant fish dudes somewhere in here too. They're harder to kill, but don't move, and I can't find them anymore.
 * The Black Rabbite of Seiken Densetsu 3 is just a palette swap of the conventional Rabbite. It's also the most deadly thing in the entire game.
 * Pokémon, in a way. While there aren't any unpredicted Boss In Mook Clothing opponents, at certain points in the games roaming Bonus Boss Pokemon appear. Which is fine...unless you're training up a lower-level team when you encounter them. Ugh.
 * On top of that, the Vs Seeker. While normally it's just a simple rematch, your opponent can sometimes have tricky teams.
 * And a special mention goes out to Bronzor, and its evolution Bronzong. The ONLY super-effective move types against it are Ground and Fire, and almost everything else is fairly useless. In later areas, they can be up to twice the level they were before, leading to a very sudden defeat if you don't have a really strong Pokemon as backup.
 * And you can only have one of those super-effective types at a time. If it has the ability Heatproof, Fire is blunted. If it has Levitate, Ground won't touch it.
 * Taken even further in Mystery Dungeon, where Pokémon have both of their abilities at once. Yes, that means that Bronzor and Bronzong have no weakness at all there.
 * They also learn some really annoying moves. Fortunately, they're so slow you can usually run away from them. But God help you against Lucian's Bronzong in Diamond/Pearl/Platinum.
 * Also, Ponyta. It's always encountered in grassy areas, usually where you expect Grass-types or, worse, Water-types (so that you're using Grass-type which is weak to Fire), has wicked high Defense for its level, and always has the move Stomp, which does insane amounts of damage for the low level Ponyta learns it at. Often decimates a low-level team you're trying to train up - and worse, is so fast it's hard to run away from.
 * Ace Trainers are often Boss in Mook Clothing, because they tend to have good Pokémon, often higher-level than most trainers in that area, and use better strategies.
 * In Pokémon Ruby and Sapphire/Emerald, there's a female Cooltrainer on Route 120 that most players tend to desparately try to avoid making eye-contact with when passing through the route for the first time. The reason why? She carries a Milotic. Ordinarily a powerful Pokémon, thanks to monstrously high HP and Special Defense stats, this one also knows Refresh, Recover, and Water Pulse. It's tough enough to take Thunderbolts to the face and shrug it off with Recover, and Refresh prevents you from wearing it down with Poison or Burns (and any status that doesn't get wiped triggers the Defense-Boosting Marvel Scale ability). Water Pulse causes Confusion at a relatively high rate as a side effect and it's damage is basically supercharged thanks to Same-Type Attack Bonuses and the rainy weather in the area. Basically, either the fucker goes down in one or two rounds, or you WILL get your party wiped.
 * In Pokémon Diamond and Pearl/Platinum, there is a Hiker named Alexander on Route 208, who you can't reach until you get Rock Climb, and that is the only right thing. He has a level 40 Probopass, with the moves Block, Thunder Wave, Sandstorm and Rock Slide. If you have anything that is not Fighting-type or equipped with a Fighting move, you'll have a tough time taking him out, because Probopass have gargantuan Defense.
 * Let's not forget the infamous Level 16 Raticate in Pokémon Red and Blue. While going through Mt. Moon, the player encounters a Team Rocket member with said Raticate that knows Hyper Fang. At that point in the game, the move is most likely a one or two hit KO on anything in your party. Plus, Raticate is pretty fast as well, so pray it doesn't use Hyper Fang when it strikes first.
 * There's also Wild Dragonite, Metagross AND Tyranitar in Pokémon Black and White.
 * Also in Pokémon Black and White, post-game you gain access to a location known as the Challenger's Cave. Aside from a few items, some higher-leveled Pokemon from non-Unovan regions, and a few trainers, the place is nothing special on the surface. However, while going through the cave you can encounter the trainer Veteran Shaun. He has a party of six powerful Pokemon, including Gyarados, Excadrill, Gigalith, and even Snorlax - all of which are probably about fifteen to twenty levels above your current party, assuming you dive right into the cave after beating the main story.
 * Last, but definitely not least, there is a literal Boss in Mook Clothing in Undella City in the post-game of Pokémon Black and White. Entering one of the houses gets you challenged to a Pokemon battle by the woman inside....
 * However, one of the most commonly acknowledged Bosses in Mook Clothing is Wobbuffet. It is a blue punching-bag looking Pokemon which can learn only seven attacks total and has offensive, defensive, and Speed stats that are pathetically low...until you look closer. Its only good stat is HP, which is the third highest in the game, and two of its moves are Counter and Mirror Coat, which do double the damage of the respective physical or special attack it received. It also has Encore, which makes you use the same move every turn, eliminating the need for Wobbuffet trainers to predict if the opponent will use a Physical or Special move. Even if you do knock it out, its fourth move, Destiny Bond, ensures your Pokémon is going down with it. Lastly, Wobbuffet has the ability Shadow Tag, which stops you from escaping.
 * In short, it is a monster which takes massive damage but stays alive and then does double the damage in return and doesn't let you switch to a monster which can handle it. There's a reason why this blue punching bag was the only non-legendary Pokemon who was considered too powerful to be used in competitive tournaments.
 * Wobbuffet's baby form, Wynaut is also considered uber tier, due to the fact that it starts with Encore.
 * Remember those goddamned Zubat, Geodude and Tentacool? Remember how you scoffed and shoved them aside? Well, their evolved forms didn't take too kindly to that. Watch as Golbat outspeed you, Confuse you, and Poison you. Graveler can take your hits and throw a nasty Explosion at you. And Tentacruel can pretty much tank anything you can toss at it, AND probably outspeed you as well, to boot.
 * Played more straight while at the same time being kind of inverted with Janine's Gym, where all of the Gym Trainers have Janine's Overworld Sprite.
 * Funnily enough, some of the "Mooks in Boss Clothing" are male.
 * Mega Man Battle Network 3 has an entire series of these in the form of the Omega Viruses. Every type of enemy in the game has a fourth level of virus that is super-fast, super-powerful, and pack high HP (some Omega Viruses get up to 500 HP, about the same as an early-game boss). Some will even have additional effects added to their attacks (e.g., Mettaur Omega's shockwave now cracks panels). Thankfully, they're only found in set encounters late in the game.
 * In Mega Man Legends, you can run into a Boss in Mook Clothing while exploring the tunnels connected to the subgates. After going through a bunch of rooms with nothing but Death Traps, you enter a room. Immediately, there is a crashing noise that's almost louder then the 'Bee-Boop' warning sound. After you run for your life, you get to a big room to see an upgraded version of the very first boss in the game. However, there's a big difference - the first boss had one drill; this thing has TWO. Due to the somewhat cramped quarters, its smash attacks are difficult to dodge, and they take a good chunk of your life bar away. Not only that, but it also can fire both drills at you all the way across the one large room if you get too far away, and it takes a ton of punishment before croaking! Thankfully, this is a unique Reaverbot only found in that one area.
 * The Cyclops enemies in Sword of Mana. They each have a 5% spawn rate in a single area on the correct day of the week. They are huge compared to most normal enemies, possess an enormous amount of HP, have very high stats, and will richly reward you with their high drop rate on aerolites. They're also a great source for leveling up weapon and magic skills.
 * Kingdom Hearts 358/2 Days introduces a couple of these. Invisibles have had a major upgrade from the first game, but the game warns you ("Caution! A powerful enemy is near!") so they may not count. Living Pods, on the other hand...Crazy amounts of HP and they hit like a semi truck. What looks like an easy mission becomes a pain in the ass thanks to these guys.
 * The Black Fungi from the first game count. They have low HP, but absurdly high defense, they don't flinch at your attacks, they release poisonous gas which will do pretty sizable damage to your party, and they spend about half the time encased in stone so you can't even hurt them.
 * re:Coded has the Eliminator, a recolored Defender that randomly appears in System Sectors. They can block any frontal attack or magic? Not too bad, normal Defenders can also do that. They can also teleport around the sector, and have crazy attack power. What makes them truly evil is their shield attack, which fires a fast-moving homing burst that can inflict any of the status ailments in the game. Better hope that it is not flip-foot or Level 1 Defense...
 * Harbinger, in Mass Effect 2, randomly assumes direct control of Collectors, making them into horribly powerful abominations with shields, armor, and the ability to launch explosive projectiles that can hit you even behind cover. And even if you kill him, he'll just find another body if any are still present. Did we mention that Collectors appear in swarms, so that you're likely to see at least a couple of possessed ones per fight towards the end?
 * The Scions can be quite tough nuts to crack as well, never mind when you're being Zerg Rushed by Husks and Abominations at the same time.
 * Thresher maws. There's a few of them in the first game.
 * 1) They are heavily shielded and have a massive amount of HP, which means they take forever to take down, even with the Mako's explosion gun thingy.
 * 2) They randomly burrow in and out of the ground with no pattern whatsoever.
 * 3) Their main attack is spitting acid at you, which completely bypasses your shields. It will One Hit KO your entire party...unless you're in the Mako, in which case it takes two hits.
 * 4) Even if you manage to avoid the acid attacks, there's nothing stopping the thing from respawning directly under you, in which case you might as well just restart. The game itself recommends you either run away or, if you have to fight, take it down with a tank. (There's only one thresher maw in the second game, and it's a boss. And you don't even have to kill it, you just have to survive for five minutes. But...you have to fight it on foot. Of course there's a catch.)
 * Luckily, you have access to something very important during the thresher fight in Mass Effect 2: Cover. Part of what made the threshers in the first one so hard was the fact the the terrain you fight every single one on is almost completely flat, meaning your options are dodge or die, in a game where you are none too agile. They have a discernible pattern, but you have to watch them for a bit.
 * YMIR heavy mechs have tough layers of shields and armor that you have to chew through before most powers will work on them, their machine guns can eat through shields in a matter of seconds, and they always target Shepard. In addition, they have a nasty habit of slowly advancing while pinning Shepard down with their machine guns, meaning you'll have to either sprint to another cover point or get cut to ribbons by their machine guns. Their rockets are just the icing on the cake. However, Bioware does throw players something of a bone; Combat Drones, deployed by Tali or Legion, take higher targeting priority than Shepard, getting their attention off you for a few seconds. It's to the point where in one of the loyalty missions you face two YMIR heavy mechs at once, it's a flat-out boss fight, and the sidequest where you fight three is That One Sidequest.
 * Mass Effect 3 adds Banshees. Huge amounts of barriers and armor means they take ludicrous amounts of damage before they go down. This is made worse by them being really skinny, and tough to hit. They can teleport around the battlefield, and like to wind up right next to you. Their heavy melee is a one-hit kill. They have a medium-range attack that tracks you and does damage over time. Their scream can stun you. Oh, and they're almost never alone. Some of the actual boss fights are easier.
 * Demon's Souls features at least one kind of super-nasty enemy in every world, and most of them have the ability to instantly or near-instantly kill you if you make a single mistake fighting them. Usually the dangerous enemies are Black Phantom variants of existing ones, easily distinguished by their black and red glow. The Boletarian Palace has red-eyed knights who can very easily break through your guard. The Tower of Latria has Mind Flayers, who can blast you from afar with strong magic projectiles, and shoot a paralyzing burst of electricity that lasts just long enough for them to walk up and slaughter you. The Shrine of Storms has four kinds of skeletons- long sword wielders that roll up to you and break your guard with overhead slashes, archers that fire magic arrows, golden-armored skeletons with huge swords, and black-armored ones with dual katanas. The katana skeletons are the meanest by far, since they swing their swords in such wide arcs. If you encounter a Black Phantom katana skeleton and try to block its leaping attack, you'll get to watch both your stamina and your health drop to zero in a heartbeat.
 * Digimon World Dawn & Dusk feature three Digimon per game, which appear in certain locations after the player beats a lengthy Boss Rush. The weakest of them is strong enough to wipe the floor with the strongest opponents from the boss rush. They also are extremely fast, so if you happen to run into two or three of those in one battle while unprepared, it is almost guaranteed that you'll see your whole party fall without even assigning a command.
 * This happened in the SegaCD game Vay near the end, since Working Designs "adjusted" the difficulty to the point where killing a dragon enemy was boss level difficulty and yet would when killed only give the experience of a weak enemy.
 * In Morrowind, Ascended Sleepers can be this, being nasty high-health spellslingers that pile tons of damaging effects on you. Fortunately, they're very rare, only appearing naturally once you're over level 20 (they also appear, completely unchanged, as named bosses).
 * Ditto Skyrim and its Dragons, with the exception that their appearance as random encounters is triggered by the plot rather than by character level.
 * The Highwayman from Chrono Cross, which at first just seems to be a scripted encounter. Then you find out it's got a mountain of health, sizeable defense, and an attack that blinds the whole party.
 * The Beebas as well, when you first fight them.
 * The flash game Epic Battle Fantasy 3 has the Monolith enemy class, which is nigh-unanimously considered ridiculous by any reasonable standard. All three of them have a ton of HP, resist virtually everything, have incredibly overpowered attacks in general, and have a move that is That One Attack by that standard. The first one you encounter is the Viking Monolith, whose That One Attack hits the entire party, can kill in a minimum of three hits, and inflicts the dangerous freeze condition at an obnoxiously high rate. Oh, and it can cause instant death with another attack. The second is the Ancient Monolith, which loves to pull out a move that heals 100% of the HP of the entire enemy party, including itself, right when you're on the verge of finally killing the damn thing. And then...there's the Cosmic Monolith. It can, and will, abuse its Doomsday attack that nails the whole field for upwards of 10,000 damage. This includes itself; by the way, it absorbs the attack element. And they have a random chance of spawning during the final battle. Have fun.
 * Do not forget their buffing spells. In a game where Useless Useful Spell is largely averted, an enemy that possesses a max-level buffing spell with the ability to use it on the entire enemy party is a huge Demonic Spider for that reason alone. And the Ancient Monolith can remove your buffs, too. Add all of this to what is mentioned above and...yeah.
 * Your one saving grace is that they don't null Syphon (instead being just neutral), so if you can pull it off, they can't do anything while you wail on them.
 * The final area of the game contains a fight with 2 Cosmic Monoliths. Considering their first attack is always programmed to be Doomsday, they're damn hard in any circumstance, even without the limit cap during the first run. Thankfully, all of the encounters in that area before the final boss can be avoided.
 * Oh, and the final bonus area? The fight there has one of each Monolith type. To add insult to injury, your party's maximum level under normal circumstances is 30. THEY'RE AT LEVEL 50.
 * Anyone who got any ways into the story of Vanguard Bandits will remember the horrors of the Sharking. Each one is nearly a match for your strongest units and they will outnumber you. In-universe, they were designed to kill pilots, and everyone is horrified to see them.
 * In Cross Edge, Lujit, a teensy pink dragon, straddles the line between this trope, Demonic Spiders and Beef Gate. You can most likely meet in a dungeon where your party is at most level 40. His level? Level 120. WAAAAY higher than THE True Final Boss. To make matters even worse, Lujit has both Parry and Perfect Barrier, which allow it to dodge both physical and magical attacks respectively when its HP hits 25%, meaning that the only way to damage it past that point is EX Skills. Good luck surviving long enough to use those. His attack of choice. A-Fear. Yes, the Big Bad's ultimate attack, and you can die from it this early. And to a little pink dragon no less. Lujit, however, can be easy provided you get him with a group of enemies, since you can kill them to get SP for the EX Skills. If you see him alone, however, run.
 * So, you're playing Baten Kaitos Origins? And you just got past that damn bird, so you're feeling good? Well, you're gonna saunter away from the crash site and run right into the Alraune. For starters, the flower has a ton of HP, capable of swallowing your strongest attacks for several turns. It's quite fond of 'Poison Breath', which hits all three characters hard and is likely to poison at least two of them. Its normal attacks are no slouch either, and the Mirabilis it comes with hit just as hard. Unless you're loaded for ice or fire, the damn thing can and will rip you apart. Just to add insult to injury, the overworld sprite appears in a very cramped location, making it tricky to dodge. Probably the best way to handle a party with one of these is to assemble Blazing Glacial Queen, but good luck keeping Guillo alive long enough to pull it off.
 * So, how could that be worse? Well, how about if they made it incredibly common, as in, most enemy encounters will have one. Then, make it appear with several enemies that hit hard, have quite a bit of HP, and have cooperative attacks with the thing. Buff up its stats a bit, make Poison Breath even more painful-wait a second, we just described the Queen Alraune, found all over Nekkar! Have fun!
 * The Herculean Dragon from Tarazed Core. Its attacks don't hit particularly hard (by this game's standard, at least) but that's small comfort when the damn thing buffs up its defense and heals itself faster than you can damage it, turning a quick battle into a drawn out slugfest. Not even The Apotheosis can kill this thing easily.
 * The Black Knights in Dark Souls. Non-respawning enemies who appear slightly off the beaten path, they have a lot of health, defense, and are very hard to defend against with fast, powerful attacks.
 * Prowling Demons. They are gigantic (in a game where size is a very good indicator of a monster's strength), there's only a handful of them and they don't respawn, and they are devastatingly powerful.
 * Anything that pops out of the white Monster Gates in Rune Factory: Tides of Destiny. Thankfully, unlike other Monster Gates, they don't automatically summon monsters when you get near them. If you manage to destroy a white Gate, however...
 * Anybody who expects the post-game Bonus Dungeon  to be as easy as the rest of Golden Sun: Dark Dawn is about to be slapped in the face by everything in there. Great Dragons are worst, since they're easily more difficult than most of Dark Dawn's bosses, and unlike bosses tend to show up in groups.
 * Opoona is full'' of these, as part of the game's general love of toying with the Sorting Algorithm of Evil . Although many areas have enemies in them who are stronger than usual, here are the most fitting candidates, in order of doomitude:
 * The Shredder, which is found only in one room directly before the boss in the Ruined Dome area. It has about five times as much HP as any other enemy in the area, and has more defense, too. However, because it's rare and in an area directly before a boss, most players will simply zip through the room without encountering it, and won't go back to it until an NPC encountered later on specifically clues you in that it's there.
 * The White Monk, found in the Sage's Tower, has far more HP than a normal enemy (over a thousand, which is more than most bosses), and its attacks, although not too punishing, are still something you need to be careful of. However, one of its Randomly Drops items is a big defense-boosting equipment only otherwise obtainable through a lengthy Collection Sidequest.
 * The Salamander has the most HP of any non-boss encounter period, and its attacks are murderous. To make things worse, it's often flanked with bombs (just about any attack that accidentally hits them will make them explode; one alone will more than halve your HP), and you can encounter it barely halfway through the game. There's quite a disparity in levels between when you can first encounter in and when you're actually ready to encounter it. Thankfully, it resides only in the optional Bonus Dungeon.
 * Deadliest of all is the terrifying Apocalypse II, found only in one small room in the Very Definitely Final Dungeon. It's insanely fast, and bombards you with laser attacks that knock off massive chunks of HP. Its defense is maddeningly high, and its HP is far too high for what its defense is at. And you have to beat it in under 2 minutes. Did we mention it's likely that you'll fight more than one at once, when one alone is more than enough for a Total Party Kill? Thankfully, it does give out heaps of experience, and brings you closer to Hundred-Percent Completion.
 * The unique monsters in Xenoblade Chronicles. All of them are tough enough to be considered bosses, and the sole distinguishing visual characteristic some of them have prior to being targetted is being slightly to much larger then the normal enemies in their vicinity. It's only after targeting them and seeing their level, odd name, and fancy info window that you can know for sure. They're also almost always aggressive, even if they're of a normally passive monster type, so one who has enabled the option to see monster info from a distance can potentially identify them in this manner, as well.
 * The most jarring example is

Shoot'Em Up

 * The NES game Silver Surfer literally has this at the end of each stage that doesn't contain the boss. A regular mook which just happens to be a mini-boss, taking more hits than usual, and sending extra enemies out at you.
 * A few Touhou Project stages feature a "death fairy"/"doom fairy", a single normal-looking enemy with a health bar and attacks comparable to most boss spellcards. Notable ones are one in Stage 4 of Perfect Cherry Blossom, one in the Extra stage of Imperishable Night, and two in Stage 6 of Subterranean Animism, all right before the boss.
 * Speaking of fairies, Lily White in Phantasmagoria of Flower View is not too hard to evade on her own, but when you're dodging her attacks in the middle of a fight against Shikieiki in the midst of a Level 4 attack and a crapload of portals that spawn sticks whenever a bullet passes by, you better have a bomb ready.

Simulation Game

 * Ace Combat games every now and then have random enemy pilots without the distinctive aces' callsign in the target display who nevertheless prove unusually hard to hit or shake off. It's one thing for clearly demarcated aces to give you grief, and another thing for no-names to come close to, say, Yellow 13's level.
 * X: Skies of Deception plays with this in the mission "Operation X" that lets you go up against various Game Breaker superfighters. The mook part comes from how they are piloted by normal, un-codenamed pilots . Of course, since they are in Game Breaker superfighters...
 * Joint Assault has AEGIS ships. They look like normal cruisers from afar but their twin SAMs have a much greater lock-on range than those on normal ships. Unless you grinded, you usually won't have unlocked long-range missiles to take them out with and they will almost always fire before you can, even going full afterburner.
 * X3: Terran Conflict introduces a weapon called the Plasma Burst Generator, which averts the Video Game Flamethrowers Suck trope so hard that it turns generic Space Pirate fighters into Bosses In Mook Clothing. Many are the forum threads where new players complain that they can't win against pirates with PBGs. (Of course, once you know to stay out from in front of them, they go back to being Mooks.)

Stealth Based Game

 * The Gekko from Metal Gear Solid 4: Guns of the Patriots. Initially, they only appear in scenes where the goal is to escape (the first enemy you come across is a Gekko), but they can be fought and there are mandatory set-piece battles with them later in the game, most of which are before you get the game's specific anti-Gekko weapon.
 * In Metal Gear Solid 3, if you trigger an alert at the cliff near Groznyj Grad (by sniping the patrols in the base), helicopters will be sent after you. Unlike the earlier ones, these have powerful attacks and it's nearly impossible to hit them with rockets. Fortunately, these helicopters don't have to, and most likely won't be encountered.

Survival Horror

 * Dr Salvador, Garrador, the Bella Sisters, JJ, Regenerador, and Iron Maiden from Resident Evil 4.
 * F.E.A.R. has the tough REV mechas which appear occasionally, they fire barrages of missiles, have twin miniguns and can take several shots from the rocket launcher and/or particle beam weapons. And more frequently, there's the Heavy Armor soldiers, a form of Elite Mook which has ultra-heavy Powered Armor and usually carries either a Penetrator rifle (which damages you clean through your armor) a particle cannon, or a rocket launcher. Later expansions feature ones with miniguns and riot shields. Project Origin throws Heavies with laser rifles at you, too, who can kill you in a couple of seconds if you're out in the open.
 * Thankfully, most of the Heavy Armor soldiers are terrible shots, making them somewhat easier to kill. Of course, that just makes it even worse when you get to the ones with lasers, because, inexplicably, they have excellent aim and fast reaction time, meaning that if you don't use cover, they'll cut you to ribbons quickly.
 * They get a lot worse in the third game: they are now equipped with shields that can absorb tremendous amounts of punishment (like two full clips of shotgun ammo at point-blank range), and they can teleport through walls, which they put to excellent use in sneaking around where you aren't looking. The only mercy is that they are no longer armed with lasers, rocket launchers, or miniguns...just the Penetrator rifle.
 * Overlapping with Demonic Spiders are the Replica Assassins, which are relatively rare and much tougher and more damaging than normal enemies in spite of their small size.
 * F.3.A.R. introduces Phase Casters, which have ridiculous shields (thankfully non-regenerating), a laser rifle similar to those used by the Heavy Armors, and they can teleport groups of soldiers into the battlefield. Very irritating.
 * In the original Half-Life, you'll encounter female assassins. While they aren't terribly hard, they do cloak and run very fast making them harder to kill than most mooks.
 * The sequel introduces the poison headcrab zombies. Have loads of HP, and can fling up to three five poisonous headcrabs at you, each one capable of nullifying your HP to 1 in one bite.
 * Fortunately, it mostly regenerates over a short time (as your HEV suit injects you with an antidote)...but if anything else hits you while you are at 1 HP, you are going to die.
 * Hunters in Episode Two are absurdly brutal, able to absorb entire clips of ammunition without flinching while constantly firing explosive fletchettes, and if they get close (which they will, as they are almost always fought in confined areas) their melee attacks will swiftly chew through Gordon's health. And the damn things travel in packs. The only respite is their crippling weakness to stuff hurled by the Gravity Gun, killed in three or four hits, downgrading them to "mere" Demonic Spiders.
 * Hunters do have one other weakness, if you're good enough to use it -- the car. Unfortunately, it gets worse in the final battle: the hunters are the escorts for your real enemy, a swarm of Striders.

Third-Person Shooter

 * The lambent gunkers in Gears of War 3 qualify. They have a lot more health than any other regular mook in the game with no apparent weak points, their ranged attack causes huge amounts of splash damage with an arc trajectory that often makes cover useless, they have pinpoint accuracy regardless of distance even when they can't see where you are, and if you get too close, their far-reaching melee attack causes massive damage and completely ignores cover. The fact that they're capable of wiping your entire squad on their own is made even more annoying by how they are almost never alone.

Turn-Based Strategy

 * Final Fantasy Tactics has Red Chocobos, a somewhat rare enemy unit with a hard-hitting attack, Chocobo Meteor.
 * Black Chocobos could also count. Regardless of them of having low HP and speed, their Chocobo Pellet does even more damage if you can't evade it. Dragons, Tiamats, and Behemoths can also be a pain.
 * It gets worse. The Baraius Hill rare battle. You get attacked by a team of dragons, tiamats, and behemoths at the same time. Accidentally getting the encounter is a valid reason for a reset.
 * Disgaea Hour of Darkness has a mechanic which allows you to build bossmooks. the 'Throw' skill usually allows you to reposition enemies and allies on the map quickly, but if you throw an enemy onto the same square as another enemy, they combine their levels (keeping the class of whichever was originally highest, but learing any new skills it would have at that level). You can quickly build a very innocuous looking Lv400 monster to decimate your Lv20 party unless you exploit battlefield conditions to wittle it down while keeping out of harms way, rewarding you several dozen levels worth of experience.
 * Draco Zombies in Fire Emblem the Sacred Stones. These undead dragons have a boatload of HP and have very powerful attacks that can also hit from a distance if you try to send your magic users after one. They're rarely seen outside of the Lagdou Ruins, though.

Wide Open Sandbox

 * Chainsaw users in Scarface: The World Is Yours. Bazooka and grenade launcher users, while also capable of One Hit Kills, at least went down in one shot from the Desert Eagle or sniper rifle, usually with dismemberment. Chainsaw guys? Multiple shots, making them fairly Implacable in the otherwise fairly realistic title.
 * Hunters in Prototype start off this way -- they're tough but manageable alone, but in groups, it's generally best to just get out of there -- but are demoted out of this status as you get more powerful. Shortly thereafter, the Leader Hunters step in to pick up the slack.
 * Super Soldiers, at first glance, are just larger versions of the human troops the player has been slaughtering by the truckload throughout the game. Actually treating them as such results in the player's attack being interrupted with a grab, followed by some horribly damaging wrestling move and getting tossed across the room like a ragdoll. Oh, and they can follow the player up buildings like Hunters and have an innate virus detector that sounds an alert in under a second.

Film

 * In Raiders of the Lost Ark, Indy encounters a very large German who wants to do some Good Old Fisticuffs with him. Indy opens with a Groin Attack, which is subverted rather painfully when the guy shrugs it off and decks him with one punch.
 * Dalip, also a Giant Mook, in Get Smart. Max and 99 beating on him just annoys him, while he throws them around like ragdolls without even trying. (It helps that the actor is professional wrestler Dalip Singh.)

Live Action TV

 * Kull warriors in Stargate SG-1. Their armor is impervious to everything from machine guns to staff weapons to claymores and equipped with dual wrist-mounted rapid-fire staff cannons. Killing them requires a specialized energy weapon that negates their Healing Factor. That's three out of four criteria met.

Western Animation

 * Inverted in Aachi and Ssipak. Two small mooks disguise themselves as the massive Big Bad to lure a Sociopathic Hero robot cop to their location. It works and the cop attacks them, only to be blindsided by the real villain.

Tabletop Games

 * The first major expansion to the board game Arkham Horror features the titular Dunwich Horror. If you can't prevent its arrival then a seemingly normal monster tile is added to the game. One with a laundry list of special rules. The Dunwich Horror has tons of health, can advance your doom counter, and a deck of cards that randomize its combat stats, drawn after you enter combat with it. On one turn it takes half damage and destroys all your gear, on the next it has no special resistances but instantly kills you. Defeating it gives you any card you wish as a reward.
 * Occasinally show up in Warhammer 40000.
 * Thousand Sons Aspiring Sorcerers that hit almost as hard as a full-blown Chaos Sorcerer despite being a squad upgrade for a Troops choice, especially with the new Force Weapon rules.
 * Incubi Klaivexes have a better offensive statline than most armies' HQ choices and some downright scary weapons.
 * Necron Pariahs who while drastically overpriced can still hack up most anything with ease.
 * Grey Knight Paladins. Two Wounds, toughness 4, 2+/5++ save, Feel No Pain, nasty weaponry...horridly expensive, but one Paladin outmatches most HQ choices.