Rush Boss

Boss Battles in video games tend towards two extremes. One type is the boss that take a very long time to beat, but poses little offensive threat; a boss that is a Stone Wall, in effect. This is the Marathon Boss. Then you have these—bosses that hit hard but die fast. However, these bosses are not necessarily easy, just as Marathon Bosses are not always difficult. These bosses can be Sequential Bosses, though this trait usually applies to individual forms in that case.

In game design, these models may be favoured for being more exciting than Marathon Boss-style wars of attrition, though if they die too quickly, players may be able to bypass whatever gimmick or strategy they were supposed to use simply by using an Attack! Attack! Attack! strategy. In addition, their attacks are usually difficult to dodge, since, obviously, dodging attacks would negate their offensive power.

Marathon Boss is this trope's inverse. See also Boss Vulnerability; these are usually type 1s.

Note that this is not merely a boss that goes down very quickly—that usually falls under Breather Boss or Anticlimax Boss. They must be able to take down you very quickly as well. Fragile Speedster-type bosses that frequently dodge attacks do not count either, since in that case it's as if they have high defense anyway. See Get Back Here Boss for that.

Not to be confused with Boss Rush, or a boss that rushes at you.

Examples of Rush Boss include:

Most of the Brothers in Turgor, in contrast to the giant Predators, who are Marathon Bosses.
- Whaler in particular; he turns into more and more of a Glass Cannon as the fight progresses, to the point where you can kill him in one hit if enough time has elapsed. In addition, his vulnerability wheels never fall off, making him the only boss that is actually capable of dying in a single hit.
The 3DS remake of Mario & Luigi: Superstar Saga turns Ludwig from a reskin of Roy and Iggy to him using and all-or-nothing barrage against the Mario Bros.
The Bone Demon in MARDEK. It has the lowest HP of all the chapter 3 Bonus Bosses, but has very powerful attacks.
Jubei Yagyu in Onimusha Dawn of Dreams can unleash several quick and damaging swordslashes in a row, which is quite bad for your health. However, with a good defense timing you can pull an easy Issen counterattack and finish her off in two or three attacks.
Both final bosses of Alpha Protocol. One uses a series of deadly miniguns but has horrible damage resistance, while the other uses a rocket launcher but can be defeated in a single punch (although getting close enough to do so can be a problem).
Ridley in the 2D Metroid games, due to being one of the few (if not the only) boss who is always vulnerable to attack. However, you usually fight him in a cramped space, and his attacks are both hard to dodge and powerful.
For Alundra, the US localization team specifically noted that they tweaked a few bosses to have more attack power and less HP than in the original Japanese version, because they felt some of the Boss Battles were more tedious than challenging.
In the flash game LARRY and the GNOMES, the Purple Monster boss has the least health of all the bosses; however, its attacks reduce a lot of health with a single hit, it attacks very rapidly, and its charge can kill you quickly if you don't dodge it.
Bushido Blade: The game's intent of realistic combat (i.e: no lifebars) effectively means that any battle can end in just one clean strike against your opponent.
In contrast to the series's love of the inverse, most boss fights in Final Fantasy V are of this trope. The first legal and decent release of the game outside of Japan was on a portable system, which was suited well to this trope, luckily.
The duel with Luca Blight in Suikoden II. Thanks to the prior Sequential Boss fight, he only has a sliver of health left, but he's still strong enough to kill you in two attacks.
Many of the DPS Race raid bosses in World of Warcraft have enrage timers that are notably shorter than bosses who are more of a battle of survival (typically 5 or 6 minutes, compared to standard 9-10 minute enrage timers), and the greatest danger is most often killing them before the timer expires and they start one-shotting the raiders.
Odin is a common Rush Boss in the Final Fantasy series as a whole, since he will generally give you a short amount of time to kill him before he uses Zantetsuken (which is either an attack that is almost impossible to survive or a Nonstandard Game Over). At the same time, he tends to have less HP than bosses of equivalent difficulty.
Most of the key bosses in Diablo II are marathon bosses (including all the Act Bosses except possibly Andarial, who's a bit of a half-way house), but the mid-act boss in Act 2, The Summoner, is a classic Rush Boss. He's extremely fragile, going down in two or three hits, but depending on your build he can easily One-Hit Kill you, at least on Normal difficulty. He also has fantastic range (well over your character's sight range), meaning new players often die to him before they even see him.
Elec Man and Ice Man in Mega Man. Both of them can destroy Mega Man in three hits, but Mega Man can destroy them in 3 hits if he uses the correct weapon.
In Final Fantasy Tactics, most Lucavi, especially Velius, can be killed relatively quickly, but can, on the other hand, very quickly obliterate you as well.
In The Legend of Zelda the Wind Waker, the battle between Link and Cyclos lasts only 30 seconds, but that time is decisive. If you fail to quickly shoot three arrows to Cyclos, he will use his cyclone to take you away to a random part of the Great Sea., forcing you to look for him again for a rematch. And if you aim for 100% Completion, then you will also need to take a picto shot to the opponent before defeating him, otherwise you will never have another chance.
The Demon Wall in Final Fantasy IV, being an Advancing Wall of Doom in boss form, is naturally one of these.