Ring Out Boss

A Sub-Trope of Puzzle Boss, and often a Bullfight Boss, the Ring Out Boss is a type of Boss Battle where the boss himself cannot be just defeated via damage, but has to simply be knocked or thrown back into a dangerous substance or obstacle to cause damage. Very much the Boss Battle type used when the hero fights the Implacable Man or a character with Nigh Invulnerability.

There are two types of this boss:
 * Type 1 is a boss which cannot be defeated by anything other than knock back, your attacks don't directly hurt said foe most of the time, or don't take them down for good, and you have to try to make it so instead of wearing down a health bar via lots of damage, that the impact from your attacks knocks them back into something dangerous to the boss.
 * Type 2 relies on a bit more force, and actually picking up, carrying and throwing/dropping the boss into the deadly substance or obstacle.

A subtrope of Convenient Weakness Placement, and very much a subtrope of Ring Out, as that is the aim in one of these battles—albeit often with a foe who can come back a few times before being killed. Related to Boss Arena Idiocy, as it's only due to the dangerous and (for the enemy) stupid design of their battle arena that they can even be killed at all.

May be a Breather Boss due to many, many cases having limited physical damage abilities against the player character, and relying on trying to send the player into the same obstacle they're weak against.

Occasionally a Bullfight Boss who has to be lured to charge into the dangerous substance/location.

Type 1

 * The Mario series loves this. You've got Big Bully, Chief Chilly, Topmaniac, Roger the Potted Ghost (and Shy Guy cohorts), Big Guy the Stilted and a few others.
 * Bowser himself in SMB3 - though projectile attacks can also be used.
 * Iggy and Larry from Super Mario World, which you had to knock into the lava on a giant tilting platform.
 * New Super Mario Bros. Wii is an inversion. Lemmy tries to ring you out. Also inverted with Big Bob-omb in Super Mario 64, throwing him off the mountain will heal him.
 * The larger Cataquacks that walk over the mirrors in Gelato Beach, in Super Mario Sunshine.
 * Bloomsday/Scumflower in Wario Land Shake It!
 * The Minotaur from Wario Land, and Red Brief J. in Wario World.
 * The Sandopolis Act 1 boss in Sonic and Knuckles has to be knocked into a pit of quicksand. The pit kind of stands out in an otherwise featureless arena.
 * Sonic CD does this kind of boss slightly differently- the boss of Quartz Quadrant is stationary and more or less invulnerable to Sonic's attacks- instead, his platform slowly wears away on the conveyor belt floor.
 * That's Quartz Quadrant, only mechanical and overly industrial in the Bad Future. As for another Sonic example, Toy Kingdom, where you pretty much evade his attacks, then hit, rinse, and repeat for a couple of minutes or so, trying to knock him into the bottomless pit.
 * The Crocomire in Super Metroid is this. Also, when it does finally fall into the acid pool, it has such a horrible Family-Unfriendly Death that some players genuinely feel bad for the poor thing.
 * The video game version of Terminator 2: Judgment Day for the original Game Boy ended with a fight against the T-1000 where, akin to the movie, he was invincible but got knocked back when shot, so the idea was to knock him off the platform into the molten stuff below.
 * Non boss example: In fourth edition Dungeons & Dragons, A character can freely move another character one square, with absolutely no way to prevent it.
 * The majority of Defender powers are about forcibly moving the enemies around. With proper build, you can do this to the Tarrasque.
 * Inverted in Super Smash Bros..: Bosses are the only fighters you have to beat with something other than a Ring Out. (Bosses that are counterparts to playable characters, such as Giga Bowser and Giant Shadow Bug Diddy Kong, still have to be ringed out, with the exception of Dark Link.)
 * The Chocobo Eater in Final Fantasy X is a subversion, as you could ultimately defeat it by depleting its HP if neither side can do enough harm for the Ring Out.
 * Once you'd beaten down Liquid Snake in Metal Gear Solid to the last of his health, it would slowly start restoring. The only way to beat him is to empty his life bar and then kick him off the edge of Metal Gear.
 * The Corpser in the first Gears of War was fought on a precipice overlooking a lake of what looked like heated Immulsion. Your weapons could barely penetrate its hide, but they could cause pain. Your goal was to shoot its soft spots and force it to recoil in agony, eventually backing to the point where the precipice could no longer support its weight and collapsed, dropping the creature into the Immulsion.
 * A slight aversion of type 1 occurs in Shadow of the Colossus, as you force one of the bosses off a ledge, then proceed to stab it to death with much prejudice.
 * The Warrior from the 2008 Prince of Persia can be defeated only by being knocked him out of the ring or into a trap every time you fight him.
 * In the original (1989) Prince of Persia, the skeleton on level 3 has no life bar, and therefore cannot actually be killed. The only way to defeat it is to knock it down into a pit (twice!).
 * The easiest way to beat Ax Crazy Burner Man from Mega Man & Bass is to push him off the platform into Spikes of Doom using the Ice Wall weapon. Of course, for him, the spikes aren't fatal (though it does take a large chunk off his health bar) and you can beat him without doing this, if you want.
 * The final boss, in the first The Smurfs game for the SNES.
 * Algol in Soul Calibur IV can be defeated normally, but has an AI flaw that causes him to jump off the tower to his doom if you kneel close to the edge of his arena.
 * Notably averted with Night Terror in Soul Caliber 3 where uniquely of all enemies if you knock him off he just flies back in.
 * The first boss in Jazz Jackrabbit II.
 * In the DS Version of Lego Batman, Bane is totally immune to your attacks- the only way to beat him is to make him run into stuff and stun himself so you can drop things on him.
 * The Sumo boss in Vexx. The first go around, it's simply a matter of knocking him back a lot, but in his second battle, he becomes a much more dangerous Bullfight Boss whose arena steadily grows smaller as you fight him.
 * Chance in the final battle of Syphon Filter 2 is wearing an indestructable armored suit, so you need to shoot him with a shotgun to knock him into a helicopter's spinning blades.
 * The final boss in the Bad Ending path of True Crime: New York City has no health bar; instead you have to punch him across a subway car and use a finishing move to knock him out the rear door.
 * A lot of boss fights in the Double Dragon series feature a convenient nearby pit (often with a conveyor belt leading into it) that you can knock the boss into if you don't feel like spending several minutes beating down his health bar. Beware, bosses can do the same to you.
 * The final battle in the Lord of the Rings: The Return of the King game is like this.Frodo fights Gollum "Neo vs. Smith" style, with the objective being to knock Gollum off the edge into the lava.
 * In The Matrix: Path of Neo game, in your first fight with Agent Smith he's invincible (as you are not yet "The One"), so you need to throw him into the path of a speeding subway car to beat him.
 * Not exactly a boss, but this is one way to fulfill the Lord British Postulate vis-a-vie the otherwise invincible Sergeant Johnson in Halo 2. In the first level, punch him into the airlock and off the space station into the void of space to kill the guy.
 * In The Chronicles of Riddick: Assault on Dark Althena, the final boss is a one-on-one duel with the female Commander, who's wearing a Bubblegum Crisis-style suit of Powered Armor. You can't damage her normally, so to defeat her you need to knock her down a nearby elevator shaft.
 * Belcha, the first boss of Donkey Kong Country 3: Dixie Kong's Double Trouble, is a large barrel which must be pushed into a lower portion of the floor at the end of his room. You don't have the leverage or strength to do so, and thus you must feed him beetles that occasionally fall from the ceiling - Belcha's belches steadily push him backwards whenever he eats one. Curiously the pit contains no hazards of its own and is no deeper than Belcha is tall. Considering Belcha's lack of mobility, however, the poor chap will never escape his comitragically small ditch.
 * Squirt from the same game is an inversion; he tries to ring you out. You kill him directly with damage, but he cannot damage you; instead, he tries to knock you off the ledge you're on by spewing streams of water at you.
 * The first boss in Spyro: Year of the Dragon is Buzz, who you must defeat by knocking him into the lava surrounding the arena. Your attacks have no damaging effect at all- all they do is knock him backwards. Knocking him into the lava makes the way clear for Sheila the Kangaroo to push him deeper into the lava.
 * The fight against Papes in The Legendary Starfy features this. Papes uses a big shield, so Starfy has to spin at him until he drops out of the pool of water in the middle of the room and hits a spiked wall. Doing this fight two-player allows one character to spin from the front and the other from the back, so it is theoretically possible to beat him without the ring out.
 * In Chapter 7 of StarTropics, there's a robotic alien who can't be damaged directly. To kill him, you have to use your attacks to push him back far enough to trip a switch in the floor. This makes part of the floor disappear. Once that's done, you have to keep using your attacks to push him back until he falls off the floor into the void.
 * The giant spider boss of Alundra 2.
 * About giant spider bosses, Phantom from Devil May Cry will fight you three times. If you defeat him the third time as usual, he will break a skylight and fall over a statue that impales him. But one of his attacks, a big jump, can be avoided at the last second while YOU are over the skylight. Do it a few times and Phantom will break it so voilà, instant death without breaking a sweat.
 * In King's Quest Mask of Eternity, the only way to defeat the skeleton with the chainmail in the Dimension of Death is to knock him back until he falls off of the tower you're fighting on.
 * The "Larries' Lament" boss in Super Meat Boy. Being that it's Meat Boy, you can't even knock them back without dying. You need to stand near some giant sawblades (probably dying a few times in the process) and then move so the Larries will jump into the saws without killing you in the process.
 * In Killer Instinct 2/Gold, the only way to defeat Gargos is a Knock Off.(A.K.A. Ring Out) He just comes back with more health, and you don't get healed at all if you beat him using regular HP destruction.
 * In the first Boktai, you fight Muspell, who is very much a Bullfight Boss. While you can just attack him normally, dodging his charges to have him roll into the nearby lava will make the fight end a lot faster.
 * A variant in Dawn Of War 2: Retribution, one campaign scenario has an Ork Battlewagon that can't be killed effectively by any method other than the recommended tactic of leading it into explosives.
 * Cyclops in Dark Messiah can only be killed in a realistic amount of time by stunning them with the scenery (or a siege weapon in their first appearance), then taking out their eye. They can be taken out by mundane means, but it will take forever, and only mage spaming lighting spells has a real chance of doing it without cheating.
 * The Legend of Zelda Skyward Sword has the first phase of the final battle with Ghirahim-he creates an aerial arena for you and he to fight on, and as can be imagined, you need to knock him to the ground.
 * An earlier case would be Scervo, the robot pirate miniboss of the Sandship, who is fought on a narrow gangplank and must be gradually pushed back by your sword attacks until he falls off of it.

Type 2

 * Dangoro from The Legend of Zelda: Twilight Princess.
 * Partial example: Defeating Jahalla in The Wind Waker requires throwing the boss into spiked columns lining the arena before finishing off the poes that make up its body.
 * The Minotaur/Bull boss from the original Wario Land.
 * All of the Bowser fights in Super Mario 64 are type 2 that resemble type 1 fights. You have to avoid throwing Bowser off the cliff, but rather throw him into the bombs surrounding said cliff.
 * Subverted by the boss fight against the big Bob-omb in the first world of the game. You encounter him at the top of a mountain and he is defeated by picking him up and throwing him, but if you try to throw him off the mountain (as your first instinct might be) you will do no damage, and the Bob-omb will leap back up to the top and will chastise you for fighting cheaply. To damage him, you must throw him down onto the very ground (the top of the mountain) that you're standing on.
 * Every single enemy in Legacy of Kain: Soul Reaver if you're unarmed. You can only stun them, then proceed to throw them into fire/water/spikes/sunlight.
 * The Sentinel in Iji, which you have to use as a soccer ball kick into electrified force fields. Though as it happens, it is possible to kill it with normal methods; it's just really hard.
 * In The Lion King game, the only way to defeat Scar is to physically throw him off the top of Pride Rock. He'll actively fight you until you beat him down hard enough, but he'll just stand there panting and occasionally hit you until you throw him clear off the rock.
 * Crow in Def Jam: Fight For New York is best killed by slamming him into a window until it breaks, sending him out it.
 * The World of Warcraft achievement "Ring Out!" is another inversion. If any of the players leave the rectangular stonework in the middle of Daakara's arena, they fail the achievement.