[[quoteright:350:[[VideoGame/WarioLand4 http://static.tvtropes.org/pmwiki/pub/images/warioland4_spoiledrotten_488.png]]]]
[[caption-width-right:350: [[SugarWiki/SweetDreamsFuel First half of battle]] -> [[NightmareFace Second half of battle]]]]

->''I have not come this far to be stopped! The future I have planned will not be jeopardized! Now, you will taste true power!''
-->-- '''Kael'thas Sunstrider''', ''VideoGame/WorldOfWarcraft'' (halfway through the boss battle)

When you bring the videogame boss down to its last few hit points, it gets mad and begins using the more powerful attacks in its arsenal. One wonders why it didn't just use them from the beginning.

Sometimes, this is sequential. The boss turns red at the two-thirds or one-half mark, then when it reaches a third- or quarter-life, Turns ''redder'' and the effect doubles yet again.

Almost makes you wish ''you'd'' [[CriticalStatusBuff suddenly get special powers by losing...]]

----

[[foldercontrol]]

[[folder:Enemy Examples]]
* One of the earliest examples of this is ''VideoGame/SpaceInvaders'', where the very last enemy ship suddenly gains an enormous speed boost and descends upon the player in mere seconds! Apparently this was originally an AscendedGlitch.
* In ''VideoGame/PacMan'', Blinky is already red, and already slightly faster than the other [[http://www.webpacman.com/ghosts.html monsters]]. When you get close to clearing a level, he gets faster, and pursues you even when the scatter timer is on. He does this in sequels, too, at least up through Pac-Mania (1988).
* The Wigglers in ''VideoGame/SuperMarioWorld'' turn red when you stomp on them once. Their face turns from happy to angry, their walking speed increases, and they chase the player.
** Bowser's clown car also does this in the FinalBoss battle: the eyes narrow and it starts slamming the ground.
* Enemies in ''VideoGame/BubbleBobble'', ''Symphony/II'', and ''Memories'' will turn red when they are the last on the screen. Their movement speed increases. They also [[TurnsRed Turn Red]] when time starts to run out in a level, or if you trap them in a bubble and don't burst it in time. It gets very annoying when Super Drunk does this...
** ''VideoGame/RainbowIslands'' does the same thing - leave them on the screen too long, or trap them under a rainbow without killing them, and they'll red up. In the unlockable NostalgiaLevel based on ''VideoGame/BubbleBobble'' itself, the original enemies are ''already'' red. Most have their attacks expanded, albeit ultimately [[CanonDiscontinuity canonically discontinuous]].
* Ditto with ''VideoGame/MarioBros'', except that the last enemy on the level turned blue. Thus, killing a blue enemy completes the level. This also happens if you leave an enemy stunned long enough for it to wake up... except they turn green and get even faster when this happens. This also happens more directly with the Sidesteppers, who get angry and move faster the first time they're bumped.
** Given a ShoutOut in ''VideoGame/GoldenSun'': Turtles and crabs moving around the field in a coin-tossing game would progressively [[TurnsRed Turn Red]] (in the same colors, even) and move faster if hit by the coin.
* Most of the enemies in ''VideoGame/GodHand'', including the bosses, go all red in the face and become more aggressive if you hit them hard enough. Or if you taunt them. Why would you want to taunt them? Because it helps build the LimitBreak bar (and the DynamicDifficulty).
* ''VideoGame/TheLegendOfDragoon'' color-codes the player's targeting icon according to an enemy's remaining HP; ''every'' enemy in the game will unveil at least one new attack when it's reduced to half its maximum HP (when the targeting marker turns yellow).
* ''Franchise/ShinMegamiTensei'' games:
** In ''VideoGame/ShinMegamiTenseiIIINocturne'' and ''VideoGame/DigitalDevilSaga'', some enemies have a type of move that effectively gives them two to four free actions. Random encounter enemies will often use it when they are the last one remaining, and bosses use it at certain points to power up and kick your ass. That being said, not all enemies have the courtesy to wait turning red before using that kind of move. While most enemies of this kind are generally courteous enough to avoid using it more than once per attack phase, at least one boss, [[spoiler:Mot]], is infamous for being fully capable of spamming this move as his turns dwindle, increasing his magical power, and using a high-damage move that cannot be resisted. [[RocksFallEveryoneDies You can predict what happens because of this]].
* Ratton viruses in ''VideoGame/MegaManBattleNetwork'' became angry if struck once and not killed, increasing their movement speed and dodging rate and firing off two homing bombs instead of just one. They didn't turn red, but they put on little angry eyes. If you happened to hit them again, they'd become nigh-impossible to track, fire faster, and in some cases fire off their bombs in groups of ''three''. Of course, they also had significantly less HP than their peers in the area, so it was mainly just to punish careless players.
* The Abductors of ''VideoGame/FreedomWars'' are tough to begin with, but after breaking open their pods and rescuing the citizens trapped inside, they start to glow red and fight more aggressively to take back the citizen you rescued.
* While more minibosses than anything else, Darknuts in ''Franchise/TheLegendOfZelda'' games routinely do this. It's somewhat justified because the player's attacks at first only damages their ''armor''. When they lose it, they get faster. In ''VideoGame/TheLegendOfZeldaTwilightPrincess'', they also throw their heavy sword or mace at Link and then draw a rapier, adjusting their combat tactic to a more agile approach.
* In ''VideoGame/DevilMayCry'', on the hardest difficulty level, every enemy can Devil Trigger if not killed fast enough. This makes them tougher, faster, much more aggressive and sometimes grants them new moves. Not only that, but in ''3'' they will also devil trigger if you kill two other enemies while they're present, on the highest difficulty level, that is. On easier difficulty levels they'd just get scared. ( Which is just as awesome. )
* Lots of melee enemies in ''VideoGame/WorldOfWarcraft'' are prone to this. Most of them will actually turn red and grow larger when it happens. The effect is generally called "Enrage", "Frenzy", "Berserk" and other similar words, and generally has the effect of increasing the enemy's damage and attack speed. Some variations of it are more sophisticated: some Ogres, for instance, will have their damage increased by a LOT, but their attack and movement severely decreased. Caster mobs generally don't turn red. Bosses have more complicated examples, see below.
* In ''VideoGame/ChronoTrigger'', the Gold Eaglets in 65,000,000 BC do this literally. There's also Mother Brain, who will go berserk if you destroy her healing monitors. She gradually gains boosts to her attack and defense, meaning she'll become literally impossible to kill if you let the battle drag on too long. These aren't the only examples, of course, but they're the most notable.
* In one of the last updates to the {{roguelike}} ''[[VideoGame/AncientDomainsOfMystery ADOM]]'', most opponents gained the ability to occasionally "fight to the death in a blind rage". A bug in the first iteration of this trait sometimes made them commit suicide instead.
* In ''VideoGame/MonsterHunter'', most large monsters have a "rage" mode that they go into when they receive a certain amount of damage, which increases their speed and damage output and occasionally makes them start using new attacks. However, unlike most of the examples on this page, the monsters in ''Monster Hunter'' will eventually calm down over time. A couple of bosses actually become reckless when they get enraged, leaving them vulnerable to abilities which otherwise don't work on them (Though the majority of them become immune or resistant to the effects of traps and flash/sonic bombs). Certain monsters like the Gigginox and Deviljho also change their weak spots while they're mad.
** Trouble is, the more health they lose, the easier it is to knock them back into rage mode. (i.e. the monster goes into rage the first time after 5 minutes of a beating and calms down. He goes into rage a second time after only 2 minutes.) This continues until a single hit will put them into rage mode. This is usually a sign that the monster is about to die.
** Some monsters also have additional levels of redness beyond the universal Rage state. The Magala monsters can enter a "Frenzy" when pushed hard enough, for instance. Another example is [[CanisMajor Zinogre]] can charge itself with Thunderbugs until it reaches a full charged state, [[ShockAndAwe electrifying its attacks]]; it also never tires out of its Charged state, but unlike Rage, it loses its charge when it's been staggered enough times.
* One mission in the Challenge Tower mode of ''VideoGame/MortalKombat9'' has the player, as Noob Saibot, fighting a version of Smoke whose uniform and hair periodically become red. When that happens, Smoke gains a status buff, doing extra damage for about five seconds. This is handwaved by the game as an effect of Shao Kahn's brainwashing.
* The Berserker enemies in ''VideoGame/NinjaGaiden Black'' were white, skeletal knights carrying a BFS around like it was nothing, and were generally DemonicSpiders normally. When pissed off, they turn black, and ramp up their ridiculousness even further. Definitely a BossInMookClothing.
** Also, Ogres were freaky monsters wearing triceratops skulls as masks. Break 'em, and they flip the hell out. Like the berserkers, they were tough as nails ''before'' flipping out, and only get tougher.
* All enemies in ''MendelPalace'' do this if [[StalkedByTheBell you take too long to complete a level]].
* In ''VideoGame/PlantsVsZombies'', the newspaper zombies will get angry and start to move faster once you've shot at them enough to knock the newspaper out of their hands.
* ''[[VideoGame/DarkCloud Dark Chronicle/Dark Cloud 2]]'' has this with the "Rage counters". On each enemy, there is a series of red tokens over it's health bar, and it's a different amount for each enemy ('''usually''', the lower the count, the lower the relative defense). Every time you hit it or, if you are using a machine gun, shoot it a certain number of times (it's somewhere between 5 and 10), one of the counters goes away. If all the counters go away, then you better start fighting smarter or run, cause its attack level will effectively '''''QUADRUPLE!'''''
* In ''VideoGame/KingdomHeartsII'', the Hot Rod heartless will charge in a berserker rage once their HP is low. Most times they strike you from where you're not looking. (This is a real pain at higher difficulties if you're at a lower level).
** The Large Body heartless similarly go berserk at low HP and start bellysliding after you at an astonishing speed, but can be stopped by blocking and/or using a reaction command on them, unlike the previous example.
** The aptly named Berserker Nobodies also do this, repeatedly using an annoyingly long, unstoppable combo on you that renders them nigh impossible to hit with anything but magic while they're performing it, and only giving you a few seconds to land a combo of your own between each assault.
* Some of the Dream Eaters in ''VideoGame/KingdomHearts3D'' like the Hebby Repp, Pricklemane and Zolephant will turn bright red once they've received enough abuse, granting them an increase to their speed and attack power, along with upgrading some of their attacks. When used as allies, the appropriate disposition can make them start off every battle in this state.
* The ''VideoGame/{{Kirby}}'' franchise has included Scarfy, an enemy that looks like a floating ball with wiggling cat ears. If you try to inhale it, it will take on a more monstrous appearance and start pursuing you. Previously it was stationary, if harmful. It can be defeated only by [[PowerCopying copy abilities]], sliding, or throwing something at it. It also has a penchant for [[ActionBomb blowing up]] after chasing you for a certain length of time.
** Scarfies were featured in ''Anime/KirbyOfTheStars'' as well, and naturally, trying to eat them didn't work there either.
** There's another enemy in ''Kirby's Dreamland 2'' and ''3'' that would remain dormant unless Kirby was riding on one of his friends, in which after getting too close would put up the [[NightmareFuel scariest face ever]] and chase after Kirby. Oh, and it's a OneHitKill to the animal friend.
** In ''Kirby and the Amazing Mirror'' there's an enemy called the Snooter that literally turns red if you don't kill it in one hit.
* In the web RPG ''VideoGame/AdventureQuest'', the Deery enemy is a small, cute deer that does not cause much damage. It seems pretty harmless, apart from its suspicious [[ElementalRockPaperScissors resistance to Darkness element damage]], which is a trait common to things such as the undead. However, when it loses about half of its HP, it will suddenly undergo a grotesque transformation into a monstrous moose [[OhCrap with bones jutting out of its body, growing horns and shaggy fur, with]] [[RedEyesTakeWarning blood-red eyes]], and the amount of damage it deals is significantly increased.
** The Moglin Uberfreak, as if being a Frankenstein's Monster Moglin wasn't disturbing enough, also does something similar after losing half of its HP.
* In ''VideoGame/QuakeIV'', Grunts will [[PowerGlows glow green]] and go into a deadly UnstoppableRage when their HP is depleted.
* In ''Franchise/{{Halo}}'', if a Brute/Elite squad leader is killed, the Grunts under their command sometimes [[TakingYouWithMe turn kamikaze]]. Similarly, Ultras and other high-ranking Elites will often rush you (pulling out an energy sword if they're equipped with one) when critically damaged, Brutes go [[TheBerserker berserk]] when their armor is destroyed or if the rest of their pack is killed, and both species will usually attempt a suicide attack if you stick them with a grenade.
* ''VideoGame/SuperCrateBox'' strives to be the best example of this trope by making any enemy that reaches the bottom of the screen drop from the top with a new (red colored) sprite. You can see it in action in [[http://www.supercratebox.com/ this video]]
* Happens literally in ''VideoGame/KillingFloor'' with the Flesh Pound. All his lights turn from yellow to red when you piss it off which means his life support just started pumping him full of adrenaline and stimulants, causing him to go berserk and live up to his name.
* In ''VideoGame/SeriousSam 3'', major biomechanoids start to fire volley of rockets when heavily damaged.
* In ''VideoGame/SpacePanic'', if an enemy is trapped in a hole but the player doesn't fill the hole in, the enemy will eventually climb out and turn into a stronger type (unless it already was the strongest type, of course). Ironically, the red enemy type is the weakest.
* In ''VideoGame/MrDo's Castle'', by the same company as ''Space Panic'', the enemy unicorns could get stronger if hit too many times, turning from red to green to blue.
* ''Franchise/ResidentEvil'':
** A number of the Tyrants from ''VideoGame/ResidentEvil'', most notably the T-103 Type from VideoGame/ResidentEvil2 have an R-Form: a violent mutation where they become much more powerful and sprout claws, tentacles, etc, at the cost of [[ClippedWingAngel loosing control and exposed weak points]]. They are fitted with [[PowerLimiter Limiter Coats]] which prevent such mutations (No points for guessing how many times these coats get burned off somehow).
** The Crimson Heads in the ''VideoGame/ResidentEvil'' remake result when a NotQuiteDead zombie gets back up. They become much faster, stronger, and... red. [[ExactlyWhatItSaysOnTheTin Hence the name.]] Can be averted by blowing their heads off or by immolating them. The [[ParanoiaFuel terror factor]] of the Crimson Heads will lead to an obsessive compulsion to ensure all zombies either die from headshots or are immolated afterwards.
** In ''VideoGame/ResidentEvil4'', starting with Chapter 2, Plagas randomly emerge from Ganados [[BoomHeadshot whose heads are blown off]], and starting in Chapter 3, they can [[OffWithHisHead decapitate Leon]].
** Similarly, the Adjules in ''ResidentEvil5'' split their heads lengthwise into ''Franchise/SilentHill''-style vertical jaws, which can also decapitate the player characters, and the some of the Plagas that emerge from Majini can detach and fly around. Uroboros speeds up significantly and shields its weak points better; the two ExplodingBarrels are best saved for this phase (if you're trying to kill it without using the furnace, so you can get its treasure).
* Take too long to destroy a [[BossInMookClothing Gardenie]] in ''VideoGame/{{PN03}}'', and it will either deploy a row of [[PillarOfLight Pillars of Light]] followed by a WaveMotionGun burst, or split in two and fire homing energy waves. Both are a OneHitKill for Vanessa.
* Big Daddies in ''VideoGame/BioShock'' gain a speed boost when their HP is half-depleted.
* Yetis from the ''Are We There Yeti?!'' DLC for ''VideoGame/OrcsMustDie 2'' literally turn red when brought below 50% health, switching from ranged attack to [[UnstoppableRage berserk charge]] that allows them to go right over the barricades.
* Mook angels from VideoGame/{{Bayonetta}} can be taunted into rage state where their attacks become stronger. It also activates when you keep damaging them for a while.
* Diedough-Goos from ''VideoGame/TheWonderful101'' turn red and go on a rampage if damaged enough. During this state their attacks are unblockable.
* In ''VideoGame/{{Borderlands 2}}'', it's possible to knock the helmet off a Goliath's head. This reveals their hideously mutated heads and angers them so much they drop their guns, regenerate all their health, and attack the first thing they see, friend or foe. They also literally turn the color red. If they kill other enemies in this state, they get bigger, stronger, and tougher, and give more XP when killed.
* In ''VideoGame/DoorDoor'', after eliminating all but one enemy on a level, the last enemy will start moving faster than the player.
* ''VideoGame/PhantasyStarOnline'' has a couple:
** Ill Gills start using a powerful charge attack when they're dropped to low HP
** Delbiters can render themselves immune to flinching when their HP drops far enough
** Gi-Gues become way more persistent with their shields at low health
* Golems in ''VideoGame/DragonsDogma'' start out with their magical seal weak points glowing blue. After a certain period of time passes fighting one, all its remaining seals will turn a deep magenta. When this happens, it will become both enraged and invincible for a good minute until it returns to normal and can be damaged again.
* In ''VideoGame/{{Vanquish}}'', if a Gorgie is critically damaged but not quite killed, it will go [[ActionBomb kamikaze]] at Sam, potentially dealing a OneHitKill if it explodes on him.
* ''VideoGame/LufiaCurseOfTheSinistrals'' has some enemies go berserk after being knocked down. They literally turn red, often use more dangerous attacks, and become much ''much'' more difficult to knock down or interrupt. They cool down after a few seconds, so it's recommended to stay out of the way until they return to normal.
** The scarecrow enemies are an amusing [[InvertedTrope inversion]]. Their alternating sleep/fire spells make them DemonicSpiders, but when berserked they'll do nothing but try to smack you with an easily-avoided and pitifully-weak melee attack.
* In ''VideoGame/{{Fallout 4}}'', [[BossInMookClothing Legendary enemies]] can "mutate", which restores their HP and gives them damage and defense boosts.
[[/folder]]

[[folder:Boss Examples]]
* The Big Boo boss from ''VideoGame/YoshisIsland''. Hit him and he inflates, making him more dangerous; hit him enough and he pops.
* More or less all bosses in the ''VideoGame/WarioLand'' series of games do this. These bosses don't all change shape, but it's a universal rule that the closer they are to death, the more furiously they'll attack and the faster they'll move. The page picture is of Spoiled Rotten, the very first boss of ''Wario Land 4''; a harmless eggplant-shaped critter who suddenly turns berserk once you've hit her enough times.
* In ''VideoGame/WarioWorld'', Red Brief J gains more attacks and his charging attack becomes more lethal as he loses health. Captain Skull is pretty much a pushover until he loses half his health, in which case Wario's punches have no effect, and stunning him is much harder.
* All bosses in ''VideoGame/{{Ys}} 3: The Oath in Felghana'' do this at half health. They gain new attacks which deal even more damage and are usually even harder to dodge than their standard attacks they begin with. Harder difficulties of the game give them ''another'' Turn Even Redder mode at 25% health left, giving them ''more'' attacks.
** In ''Ys IV (The Dawn of Ys)'', after depleting Arem's first health bar (which is [[ThatOneBoss tough]] [[MarathonBoss and long enough]]), he gains PoweredArmor and becomes even faster, tougher and deadlier. Fortunately, for his final form he is reduced to an [[ClippedWingAngel easy-to-beat]] BlobMonster. In ''Mask of the Sun'', after depleting the Centaur's HP half way, he separates from his lower body and goes ThatOneBoss on you. Also in ''Mask'', after depleting Gruda's first HP bar, he turns OneWingedAngel and also becomes ThatOneBoss.
** Zava does this in the remake of ''Ys II'' after you destroy the bat-like things.
** All of the bosses in ''Ys Origin'' as well, most notably the [[spoiler:not-quite]] FinalBoss Dalles, who has three health bars; each with a new form, several new attacks, and new strategies required to deplete them. His final form combines BulletHell, BeamSpam, [[BlowYouAway lightning tornadoes]], [[EnemySummoner two drones]] that spawn more BulletHell, [[KillItWithIce dropping balls of ice that freeze the ground]], ''and'' [[SwirlyEnergyThingy suction vortexes]] that can suck you in for a '''brutal''' [[CrucifiedHeroShot crucifixion]] / [[WaveMotionGun giant laser beam]] attack. ''All at (nearly) the same time.''
* The BigBad of ''VideoGame/ShadowOfTheNinja'' does this.
* The ''Franchise/{{Metroid}}'' series, namely ''VideoGame/SuperMetroid'', ''VideoGame/MetroidFusion'', and ''VideoGame/MetroidZeroMission'' are famous for bosses that gradually change in color, appearance, and difficulty the closer they get to death.
** Bunches of bosses in the ''VideoGame/MetroidPrime'' series do this too. Ridley is one notorious example, as are the guardian bosses from Prime 2 (Jump Guardian, Bomb Guardian, Spider Guardian...) and the final bosses of all three games ([[spoiler:Metroid Prime, Emperor Ing/Dark Samus, and DS/AU 313]]).
** Many regular enemies in ''Prime 3'' would enter [[LimitBreak Hypermode]] at random intervals. The bosses would also alternate hypermode after sustaining enough damage.
* In ''VideoGame/{{Tekken}} 6'', all characters will enter Rage mode at low health, but the boss will actually begin to ''glow'' cherry red when he's losing, and can pretty much [[OneHitKill kill you with one hit]] you at that point.
** Speaking of Tekken, Heihachi will do this in ''VideoGame/StreetFighterXTekken'', should he activate Pandora mode. Usually, the character who you're sacrificing to get Pandora mode will crumple up on the floor and the character receiving Pandora will become a purple/black mix. However, when giving Heihachi Pandora, he simply [[YouHaveOutlivedYourUsefulness throws his partner out of the ring]] and turns red.
* Every boss from ''VideoGame/FinalFantasyXII'' will do at least one of: unlocking more powerful attacks, doubling their power and toughness (effectively meaning their lifebar is 150% long) or turning invincible(!) The only practical way to defeat some is to damage them to just above the threshold, and then unleash the characters' [[LimitBreak one-use-only ultimate combo attacks]] and pray. When applied to some of the game's [[BonusBoss wicked optional bosses]], things just get ridiculous.
** Several Marks gain the hidden ability "CT=0" which allows them to throw attacks at you ridiculously quickly, once they hit critical HP. (It sets the Charge Time of all of their actions to zero, meaning attacks are repeated just as often as their animation allows. Oh, and Haste doubles the animation framerate.)
** The player can also turn red if you've unlocked certain augments, with characters having a better chance to unleash a devastating combo when on low health or suffering various status ailments.
** By end-game, every single enemy can [[TurnsRed Turn Red]]. If their hits can combo, critical health makes their combo rate skyrocket. No exceptions. Most of the beefier enemies (Bunes, Behemoths) have their attack and defense ratings jump by fifty percent. Some (Reavers, Behemoths) unlock powerful moves, and even if you kill them the attack (usually magical and area-of-effect) will still execute. Other scrappers (Abaddon, Crusader) ignore evasion while their combo rate and attack go up. Entites have, at half health, ''zero MP cost'', and then they get more abilities when they reach critical. This all is ''not counting'' what powerups the BonusDungeon versions of these ''regular'' monsters get--and let's not even start with the [[BossInMookClothing Rare Game]] monsters.
** Almost every single boss in ''VideoGame/FinalFantasyIII DS'' has extra moves that aren't used until they lose a certain amount of their health.
** ''VideoGame/FinalFantasyIV'' had the Calco and Brena dolls, which unless you manage to wipe out the last few of them at once, merge into the giant PerversePuppet Calcobrena. Even worse, the dolls have a nasty habit of using [[ActionBomb Self Destruct]] when there are only a few of either kind left, which triggers the transformation into Calcabrina by reducing their numbers.
** [[BonusBoss Enuo]] from the Gameboy Advance remake of ''VideoGame/FinalFantasyV'' does a somewhat subtle version of this when he reaches roughly half health; all damage dealt to him is halved and he begins using dangerous counter attacks. This isn't a visual change, but is rather indicated by the message "The power of the Void is increasing!"
** In fact, most Final Fantasy bosses tend to have complex scripts that dictates the boss to do different (and usually more nasty) things at lower HP. The ones listed above are just the tip of the iceberg, really (though for most of them, the powerup aren't as obvious).
* In the second ''VideoGame/GoldenSun'', the FinalBoss is a three-headed dragon. Whenever a head is killed, the boss gains access to more powerful attacks. On the other hand, it loses actions with each head, so that by the time it is down to the last head, it only has 2 actions (like every other boss.) It's also using both turns to BeamSpam you, so it's not like the fight is subtly getting easier.
* In many games of the ''Franchise/ShinMegamiTensei'' franchise, bosses tend to turn red. Some start using stronger or different moves, some call for help and so on. ''VideoGame/{{Persona 2}}'''s BigBad also changes his dialogue when you talk to him in battle. If a boss starts talking in the midst of battle, it's usually a bad sign.
* ''VideoGame/{{Persona 3}}'': [[spoiler: Nyx Avatar does this, first by having you fight him through several relatively weak patterns until you get to the Death arcana, when his defense and attack power go through the roof. He takes it even further when he breaks out Moonless Gown. And don't even mention Night Queen to some of the people who've beaten the game...]] Of course, you can just bust out [[GameBreaker Armageddon]] after he [[spoiler:shifts to Death]], scoring a OneHitKill and [[CuttingTheKnot skipping the second half of the fight.]]
* In the premiere gameplay video of ''VideoGame/DiabloIII'', the Barbarian fights the Thousand Pounder mini-boss. At half health, he turns black with glowing tattoos and becomes much faster.
* ''VideoGame/{{SaGa}}'' series:
** The final boss of ''VideoGame/{{SaGa 2}}'' starts the battle by firing laser beams, upgrades to an atom smasher after taking a bit of damage, and then eventually just starts '''launching the atom smasher at the party'''.
** During the final boss of ''VideoGame/{{SaGa 3}}'', if the player takes a moderate amount of time during the final fight with Xagor, his demonic form opens several mouths. However, for reasons fans aren't certain of, he doesn't seem to get any stronger; in fact, he becomes vulnerable to certain elemental attacks.
** The final boss of ''VideoGame/{{Romancing Saga 3}}'' creates an eclipse in the background, gains wings, and draws power from one of the four Devil Lords. If you didn't kill at least one of the four Devil Lords before this fight, you're pretty much guaranteed to lose at this point -- unless the party has nearly maxed-out WP and JP and you use the GameBreaker ([[spoiler:Zo with Dragon God Descent]]).
** In ''VideoGame/UnlimitedSaga'', the {{Sequential|Boss}} FinalBoss loses parts as you advance through the battle, losing the attacks related to those parts and starting to use new stronger ones. It also starts to get more attacks per turn. Then, at the final stage, it loses part of its... [[GiantSpaceFleaFromNowhere hmm, head?]], and also its weapons (which [[OhCrap were power limiters]]) and turns bright red. He gets a HP refill as well, which means you'll have to hit him a bit before he start losing more [=LPs=] again. At this point, all of his attacks are strong and/or painful, the strongest one [[MeaningfulName being called]] [[ThisIsGonnaSuck Overkill]].
* Cerberus from ''VideoGame/DevilMayCry 3'' gets bonus points for literally turning red.
** Phantom from ''VideoGame/DevilMayCry'' turned a brighter shade of red and moved noticeably faster right around when you had him at about a fifth of his lifebar.
** Nightmare chooses to Turn Red ''after'' you deplete its life bar for the last time. The formerly slow and predictable (and controllable) machine suddenly regenerates about a quarter of its health, breaking apart into a pulsing half-solid, half-goo mass that pelts Dante with lasers, missiles, and slugs while sucking away his power gauge and trying to eat him.
** In fact, almost all of the ''VideoGame/DevilMayCry 3'' bosses change their attack pattern or add to it after a certain amount of health is lost, usually 1/3, 1/2 and 2/3 of the life bar. Nevan's attack power is directly linked to her health, she summons more bats and lightning bolts in the same move if her health is lower. She also gets the normal pattern changes, including one that introduces a potential insta-kill life draining attack.
** Most of the bosses in ''VideoGame/DevilMayCry 4'' are examples of this, and do so again when playing on the hardest mode. For example Echidna the She-Viper; After hacking her lifebar down past the half-way point, not only does her attack pattern change, but the scenery turns noticeably stormier and Echidna herself starts glowing menacingly. [[spoiler:Sanctus]] also visibly changes halfway through the first major battle with him when he includes the involvement of the incomplete Savior.
** VideoGame/DevilMayCry 3's final fight against Vergil... "You're going down. AAARRGGHHHH!" Cue utter decimation of the player.
* Solidus Snake from ''VideoGame/MetalGearSolid2''. He's relatively easy at first, but once half of his health bar has been depleted, he says, "Very good, Jack, but this is where it gets interesting." He proceeds to shed his tentacles, begins spamming a lunging blade attack that leaves behind a trail of fire, and is generally much more aggressive.
** The Rays, once damaged enough, start using homing missiles and laser cutters.
* The Pain from ''VideoGame/MetalGearSolid3''. Once down to about half health, he takes off his mask, revealing his disfigured face. He then becomes more aggressive and unleashes his "Bullet Bees," [[BeeBeeGun poisonous bees that he shoots like bullets]].... from his mouth. It's a long story.
** [[WesternAnimation/TheSimpsons "Or what, you'll unleash the dogs? Or the bees? Or the dogs with bees in their mouth and when they bark they shoot bees at you?"]]
* [[MoreDakka Vulcan]] [[GatlingGood Raven]] from ''VideoGame/MetalGearSolid'' originally starts out stomping around the Alaskan permafrost. Shirtless. Carrying a giant vulcan cannon. After taking a bit of damage, he stops playing around and ''hauls ass''.
* [[spoiler:Metal Gear Pythagoras]] of ''VideoGame/MetalGearAcid'' literally turns red after losing both wings. Which signals the introduction of its almost-unavoidable giant laser.
* Sundowner from ''VideoGame/MetalGearRisingRevengeance'': after the last of his shields are cut off, he lets out a monstrous bellow before equipping his Bloodlust machetes and ramping up the aggression.
* In ''VideoGame/RogueGalaxy'', one boss literally turns red and attacks again immediately, being twice as hard to defeat. The game even {{lampshade|Hanging}}s this.
--> "Does he think turning red is going to help?"
* The challenge of the High Priestess in the PuzzleGame ''VideoGame/TheFoolsErrand'' comes in the form of 99 flashing buttons that need to be pressed in order. Now, you would think that this would get easier once you'd taken out enough of them that they don't overlap and jump in front of each other so often. But when the number of buttons goes below a certain number, they start jumping randomly about the screen, making this UnexpectedGameplayChange to reflex-based play that much more annoying. And when you're down to just one, it moves so fast that it is ''physically impossible'' to react to it in time, forcing you to [[MoonLogicPuzzle think outside the box]].
* Franchise/DonkeyKong::
** Most of the Kong bosses in ''VideoGame/DonkeyKongJungleBeat'' (Except ironically the last one) trigger a cutscene at half-health of them yelling. After that point the boss gets slightly faster/harder and sometimes uses a different tactic.
** Queen B in ''VideoGame/DonkeyKongCountry'' did this after every hit.
** Kruncha in ''VideoGame/DonkeyKongCountry2DiddysKongQuest''. Pretty much every boss in any of the ''Donkey Kong Country'' games adjusts attack pattern progressively harder after ''each'' hit. King Zing Sting in ''2'' can't be hurt while colored red.
** Both Mugly and Thugly in ''VideoGame/DonkeyKongCountryReturns'' progress through [[RuleOfThree three stages]] as you fight them; both turn red and crank up their attacks in the third stage.
** Most bosses in ''VideoGame/DonkeyKongCountryTropicalFreeze''. The fifth boss has an interesting justification. Every time you hit him you knock him into a pool of juice, dying his fur darker each time.
* ''Franchise/SonicTheHedgehog'':
** The "Pinch" mode of the more recent handheld ''Franchise/SonicTheHedgehog'' games, where the boss music changes, the attacks get harder, and, in ''[[VideoGame/SonicAdvanceSeries Advance 2]]'', rings stop appearing.
** Continued in the ''VideoGame/{{Sonic Rush|Series}}'' games, where this is known as Allegro in the music changes. The Ghost Titan from ''Sonic Rush Adventure'' will start the event mode against him in Allegro mode. It's [[ThatOneBoss not fun.]]
** Zero from ''VideoGame/SonicAdventure'' does this if Amy hits him too many times when it's chasing her. When you fight it for the last time, it will also turn red every time it takes damage.
** The Biolizard from ''Sonic Adventure 2'' does this by changing its attack pattern ½ the way through ''and'' ¾ the way through.
** Every boss does this in ''VideoGame/SonicTheHedgehog4''. Subverted with the final level, which has a BossRush of all of the more vicious forms, before pitting the player against the FinalBoss.
* Franchise/SuperMarioBros:
** Johnny Jones, the boss of the Sunken Ship in ''VideoGame/SuperMarioRPG'', literally turns red, becomes much stronger, and [[DuelBoss challenges Mario to a duel]] when close to defeat (if you kill all his henchmen first).
** ''Every single boss'' in ''VideoGame/SuperMarioGalaxy'' does this. [[BigBad Bowser]] runs faster, [[RecurringBoss King Kaliente]] [[TennisBoss shoots more projectiles]] and [[MookMaker summons]] more Flameys, [[BigCreepyCrawlies Bugaboom]] turns red and starts flying while tossing bombs, even that friggin' [[GiantSpaceFleaFromNowhere Major Burrows]] burrows around faster and actively chases the player. And worst of all, [[ThatOneBoss Fiery Dino Piranha]] runs faster, turns more sharply, ignites his tail much faster, ''and'' leaves a trail of fire behind, and starts spraying exploding fireballs all over the place. [[NintendoHard Yeesh.]]
** So did [[http://www.youtube.com/watch?v=6jDaoR2SLGQ Raphael the Raven in ''Yoshi's Island'']].
** [[spoiler:Bowletta]] in ''VideoGame/MarioAndLuigiSuperstarSaga'' turns black once damaged enough, assuming an entirely new attack pattern as well as becoming [[TheSpiny hazardous to jump on]].
** ''VideoGame/MarioAndLuigiPartnersInTime'' has Princess Shroob quite literally Turn Red in her boss fight, making her attack more quickly and more often.
** ''VideoGame/MarioAndLuigiBowsersInsideStory'' features a ''heroic'' (well, [[VillainProtagonist kinda]]) example: Bowser gains a status buff called 'Rage' when he gets hit too many times, which makes him turn red and increases his damage output at the cost of him also taking more damage.
** In ''VideoGame/MarioAndLuigiPaperJam'', most bosses will do this literally at half HP (With accompanying steam), which makes their attacks harder to avoid, more damaging, and more frequent. When facing multiple opponents this is based on ''combined'' HP, and affects all of them.
** In VideoGame/SuperMarioGalaxy2, nearly as many bosses do this as well. Gobblegut actually does the whole train whistle with steam coming out of it thing, King Lakitu and Prince Pikante get visibly angry and turn red, Peewee Piranha turns red [[note]]but if you approach him from the front turns and runs away [[TooDumbToLive exposing his weak point]][[/note]], Squizzard brings out two [[{{BFG}} gigantic bomb shooting cannons]], Sorbetti generates red steam when annoyed and gets quicker, etc.
** The Phantamanta in VideoGame/SuperMarioSunshine splits into smaller and faster parts when sprayed with enough water - Getting every part down to its smallest level makes the manta rays turn reddish pink and chase you instead of just floating about.
** Fighting boss characters in ''VideoGame/MarioParty 9'' and ''VideoGame/MarioParty: Island Tour'' uses this trope when their health gets below half. They'll either attack/move faster or have new attacks. They'll also throw a tantrum as well.
* ''VideoGame/MegaManPoweredUp'' gave every boss a special attack that turned the boss invincible, did huge damage unless dodged, and would be used on the player any time the boss was under half health.
** In general, not too many bosses from ''Mega Man'' did this, but for the arcade games, they all did.
** Starting with ''VideoGame/MegaMan7'' and the ''VideoGame/MegaManX'' series, bosses reacted differently to their weakness. Some of them would appear to enter a special invulnerable animation, then unleash their special attack.
** In ''VideoGame/MegaManX3'', every boss will Turn Red at 50% health, either changing the battlefield (Gravity Beetle will open a persistent black hole at the top of the room that affects jump physics and injures X if he touches it), or adding a new attack to their pattern (Tunnel Rhino gets an invincible dash attack).
** In ''VideoGame/Rockman4MinusInfinity'', the Robot Masters changed their palettes, changed their patterns and made them faster.
* In ''VideoGame/KidIcarusUprising'', [[spoiler:when Pit goes up against Medusa, she assumes her more humanoid form at first. Once she takes enough damage, she reverts to her true {{Cyclops}}-esque NightmareFace form.]]
* The Twin Freaks fight in ''VideoGame/DynamiteHeaddy'' has an interesting take on this. You're running through a maze, Twin Freak chasing you. Normally he's green, smiling, and relatively slow (although he does shoot projectiles). But there are switches in the maze that flip the screen. And in the flipped version of the maze, Twin Freak is red with an angry scowl, invincible, and moving ''much'' faster. You have to avoid him until you can flip the maze again and turn him back to green.
* In ''VideoGame/TreasureOfTheRudras'', all bosses gain shades of red/dark red/purple to show how much life they have left. The darker the shade, the closer they are to death.
* Almost any arcade BeatEmUp, especially the ''Franchise/TeenageMutantNinjaTurtles'' ones.
** ''VideoGame/XMen'', too.
** Quite literally in ''VideoGame/TheSimpsons'' arcade game.
* As if it wasn't difficult enough to get and fight it, the [=TzTok=]-Jad monster in ''VideoGame/RuneScape'' calls a slew of healers the moment he hits half HitPoints. And if the player can't take him or them fast enough, they will heal him to max health, and reappear when he is at half HP again.
* The bosses in the first ''VideoGame/BreathOfFire'' game will recharge a sliver of life, which takes more time and effort than the previous entire life bar to get rid of. The later games 'solved' this by hiding life bars of enemies you haven't beaten before.
** Some, in particular the Grimlin and Horntoad, would "get mad" at the party and ruthlessly spam hit-all magic attacks that became harder to cope with, as there was only one cure-all spell in the game (and it was unlikely the player would have learned it at either point in the game).
* There are probably a number of of MMORPG examples. In ''VideoGame/WorldOfWarcraft'', for example, most instance and raid bosses will have some variant on this, whether [[FlunkyBoss summoning more minions at various health levels]], going berserk or pulling out an especially nasty one-time move. Most raid bosses have a time limit, after which they simply [[UnstoppableRage go nuts and kill everyone, no exceptions]]. Others get more and more powerful as time passes, eventually overwhelming their enemies (sometimes called a Soft Enrage, while the strict time-limit variant is called Hard Enrage).
** The earliest one encountered is probably Herod; he is otherwise a straightforward tank and spank with occasional "avoid the whirlwind", but things get interesting once he is brought down to 50% hit points.
** An interesting variant is a boss that simply becomes immune to all damage with a shield. The shield can only be broken by luring him into special fires. ''Then'' he Turns Red. Bosses have in the past had ''three'' different types of this effect, which used to ''all'' be called Enrage, but have since been clarified and distinguished from each other. Throughout the fight, you might see the boss Enrage ("Boss becomes enraged!"), which can be dispelled by your friendly neighborhood hunter before the boss renders the tank into fine paste or exhausts the healers. The classic [[DesperationAttack Frenzy]] ("Boss goes into a frenzy!") happens when some bosses are at low health, and must be powered through and the fight ended quickly. Other bosses have a hard timer that cause them to Berserk ("Boss goes into a berserker rage") if you take too long, which usually makes them [[OneHitKill mash the tank for 3x his HP bar]], then move onto [[ThereIsNoKillLikeOverkill clothies]] and...yeah.
** Jan'alai in the 10-man Zul'Aman raid has a two-stage version of this. Five minutes into the fight, his damage and attack speed increase by 50%, making things harder but not necessarily unmanageable. Ten minutes into the fight, he goes berserk and his damage increases to the point where he can wipe the raid in seconds.
** Some bosses are specifically scripted to use other [[DesperationAttack eleventh-hour abilities]] when their health drops to dangerously low levels. Some of these abilities are so JustForFun/{{egregious}} that they define the boss fight in question (e.g. summoning hordes of mooks or changing into a more [[AGodAmI badass form]], requiring your party to [[MoreDakka "nuke it down"]] before the inevitable happens). It is genuinely rare for a [=WoW=] boss to ''not'' be at his most powerful just prior to his CriticalExistenceFailure. Fortunately, this is generally VERY physically impressive, and makes for a very entertaining watch (Malygos blasts the chamber under you into nothingness, Kael'thas' power shatters Tempest Keep around him). Just don't get hypnotized by the awesome, or you'll end up dead.
** A rare case of a boss becoming ''weaker'' later on is Magmadar in the Molten Core. Throughout the fight, he repeatedly goes into a "killing frenzy", but after a certain period of time has passed, the game states "Magmadar becomes exhausted!" and his attack speed is reduced.
** Warlord Kalithresh is an interesting example. He will enrage only if players fail to destroy the water tank he is channeling from in time.
** Ulduar introduced another form of this, bosses that become much harder when certain conditions are fulfilled. This also grants the players better rewards... if they can handle the challenge.
** DualBoss encounters (or more) also tend to do this when one of the bosses die. The Iron Council trio gain new abilities when one of them dies, to the point that the last remaining member can be more dangerous than the original trio. Another DualBoss, a pair of giant worms, have a similar mechanic in that both use a nasty StatusEffect that can be cured by standing near a player with the effect from the other worm. The surviving worm also enrages.
** Shannox is the most recent example of this. Kill one of his dogs and he enrages, gaining attack power. Kill his second dog and he does it *again*. Get his to 30% health and his dogs go berserk and OneHitKO the whole raid (on normal mode, on heroic mode they somehow lose the ability to care).
** Fathom-Lord Karathress follows the standard "you kill my EliteMook, its death empowers me" model, but with a twist - if savvy players nuke the boss directly to get around this, he draws powers from the ''surviving'' EliteMooks to increase his attack speed and damage to unmanageable levels. On top of that, he berates you for trying to be cheeky.
** All three of the [[WolfpackBoss Iron Maidens]] will turn red as soon as any one of them is damaged beyond a certain threshold. The usual strategy is to keep their healths equal to ensure minimum time in the enrage phase.
** The three bosses of the Hellfire Council have their own enrage when sufficiently damaged which unlocks a special ability. The unique aspect of the enrage is that its effect remains active after the boss itself dies: A stacking debuff that reduces total health; periodic raid wide damage; and a large number of damage debuffs that can't be removed.
* All monsters, bosses included, in ''VideoGame/FinalFantasyXI'' will begin to use their special attacks more frequently (every time their TP hits 100, as opposed to randomly between 100TP and 300TP) when their HP is below 25%. Bosses frequently use their job's [[EleventhHourSuperpower 2-hour ability]] at specific HP points, sometimes more than once or for more than one job, and may begin using more dangerous special attacks at low HP. Certain notorious monsters in particular will increase dramatically in strength and defense after a time, but this is determined by actual time elapsed and not HP loss, and is meant to make it difficult for players to hold a monster to relocate its respawn time into their own time zone. This isn't intended as difficulty increase, as more often than not they become impossible to defeat when this happens until they kill all attacking players and regenerate to full health.
* A lot of bosses in ''VideoGame/CityOfHeroes''. ''Every'' Praetorian and Arachnos Archvillain, every Freedom Phalanx Hero will, at 15% health, pop out a new fancy power, usually related to their tier 9 primary power. Most of the more memorable ones involve turning on green/rainbow/blue/red backlights and being near-invulnerable for the next three minutes. Then there are the ones who can self-resurrect and force you to defeat them again.
** Bloody Stunner Chiefs. Bloody Juicer Chiefs. Bloody Tanks. Bloody Clockwork Princes. Bloody explosive enemies. (Mages, I'm looking at you. Embalmed Vahzilok zombies, I'm also looking at you.) Quite a lot of the stuff I like fighting does this...
* In ''VideoGame/RuneFactory: A Fantasy Harvest Moon'', the bosses literally become a reddish tint and attack faster and stronger after certain HP depletion. Especially lethal since it's really easy to forget that this happens, and it throws off the timing you've established that far. It's the same in ''VideoGame/RuneFactory2''. In ''VideoGame/RuneFactory3'', the bosses begin to flicker black and gain an extra-powerful attack.
** ''VideoGame/RuneFactoryFrontier'' takes that up a notch during post-main story rematches against dungeon bosses if they have already been beaten at least twice. They will go through the entire match in "tinted" mode and can easily [[CurbStompBattle curb stomp]] your character if unprepared.
* In ''VideoGame/CastlevaniaAriaOfSorrow'', [[spoiler:about halfway into the battle with Julius Belmont, he unleashes his Grand Cross attack, which causes towers to collapse in the background and tries to suck you into it for massive damage, and from then he on uses subweapons -- though he's quite difficult already even without them, such is his badassery.]] Before that battle, you face Balore, who midway through, uncovers his right eye and starts firing LASER VISION AT YOU, constantly!
** Gaibon from ''VideoGame/SuperCastlevaniaIV'' ''literally'' TurnsRed and breathes more fire when you halve his life bar; even his partner-for-life Slogra, the Dinosaur Knight, attacked faster when you break his spear. Even more interesting when you consider they both retained this trait [[DegradedBoss after they became normal high-leveled mooks]] in later games.
** ''VideoGame/CastlevaniaOrderOfEcclesia'' has the crab boss Brachyura, that pursues you up a shaft. You need to deliberately anger it so that it will break the ceilings that are blocking your way; making it turn red is not an indication of how much health it has left (though it is an indication that you're making progress).
*** From the same game, Dracula himself will adopt a different strategy later on, replacing his traditional attacks with summoning wolves and bats, draining your life, and actually walking after you.
*** Blackmore also does this. He's insanely hard already, but then he says "That was quite entertaining!" and attacks more erratically and more dangerously. In hard mode, he never says the quote and starts the fight in that mode. It's not actually that much harder, as he is so difficult anyway.
** ''[[VideoGame/CastlevaniaCircleOfTheMoon Circle of the Moon]]'' has [[spoiler:[[RivalTurnedEvil Hugh]]]], who halfway through the battle, turns on the power of evil and gets an ex skill for each of the sub weapons.
** In both ''[[VideoGame/CastlevaniaSymphonyoftheNight Symphony of the Night]]'' and ''[[VideoGame/CastlevaniaPortraitOfRuin Portrait of Ruin]]'', the [[OurZombiesAreDifferent zombie]] [[DeadPersonImpersonation doppelgängers]] imitating [[spoiler:Trevor, Grant, and Sypha from ''[[VideoGame/CastlevaniaIIIDraculasCurse Dracula's Curse]]'']] all gain new or stronger attacks when one of their allies fall in battle. [[spoiler:Sypha]] even gains the ability to re-revive [[spoiler:Trevor]], albeit as a shambling, mostly-dead shell.
*** In the battle with Richter Belmont, once his HP is halved, he'll immediately use Hydro Storm, and become stronger and more aggressive.
** Death in ''VideoGame/CastlevaniaChroniclesOfSorrow'' will change slightly, with new and deadlier attacks. Then again, Death does this in other games too.
** When it gets low on health, the Gargoyle boss in ''VideoGame/CastlevaniaBloodlines'' stops its ranged attacks and repeatedly attempts to slam into you. This actually makes the fight ''easier'' - the attacks become slower and easy to dodge, and you can get more hits in because it's no longer zooming out of range. You just need to account for the small, spinning arena, which constantly changes so as to pull you toward the boss.
* About 80 percent of the Minotaur boss fight in ''VideoGame/GodOfWar'' is a simple matter of pattern recognition, blocking, and successfully executing the necessary mini-games. Once you get to that final 20 percent, however, the damn beast loses its armor and starts launching unblockable super-attacks.
* The fourth edition of ''TabletopGame/DungeonsAndDragons'' has the "bloodied" status applied to anyone under half health. A few creatures become stronger in this state: For instance, the Angel of Valor can turn his swords into armor-ignoring [[LaserBlade energy blades]] when bloodied. Conversely, however, the players can gain special abilities that make them stronger against bloodied foes, so it may be a wash.
* Done a few times in ''VideoGame/StarFox64''. The perhaps most surprising example is the robo boss at the end of ''Sector X'', which suddenly comes back to life (even fooling the shield bar). Then again, the fact that he didn't explode like any other boss might be quite a giveaway. The second fight is, however, fairly easy, but you need to kill him fast or he'll hit Slippy, forcing you to play on the easy route.
** "I admit defeat. IF THIS DOES NOT WORK!" (Meteor boss)
** Gorgon, the Area 6 boss, activates its Rainbow WaveMotionGun.
* ''VideoGame/SmashTV'' was all about this trope, with the big boss of each stage covered in ablative amour, and progressing through several stages of aggro as the players unleashed gobs of firepower. The excesses could even be considered a parody.
* This is Kracko's schtick in the ''VideoGame/{{Kirby}}'' franchise. You'll fight him as a weird eye thing, eventually empty his life meter... and then (mid-fight TakingYouWithMe fake-out optional) face a whole 'nother life meter's worth of battle against him, now with his trademark cloud and lightning attacks.
** Kracko's hardly the only one. In at least three games, [[WarmUpBoss Whispy Woods]] becomes more aggressive after halving his lifebar -- in one instance, he actually uproots himself and starts to chase you. [[UnderwaterBossBattle Acro]] also does it in his two appearances in the franchise.
** King Dedede, at least in Nightmare in Dreamland.
** The BonusBoss / TrueFinalBoss Dark Matter does this in nearly every game it's in, too. One moment you're fighting a cloud of black smoke, the next you're [[NightmareFuel up against a giant bleeding]] ''[[NightmareFuel eye.]]''
** In ''VideoGame/KirbysReturnToDreamLand'', all of the bosses get serious and start using new attacks at half health, with a change in size and/or appearance often accompanying it. Some are more notable than others. The [[DiscOneFinalBoss Grand Doomer]] Turns Red twice: once normally, and a second time at low health that makes him NighInvulnerable. Only Super Abilities could damage him. The FinalBoss, [[spoiler:Magolor]], Turns Red FOUR TIMES for a five phase final boss fight after the traditional [[spoiler:UnexpectedShmupLevel]]. However, these phases are generally divided into two forms: The first three phases that work like the Grand Doomer, then a normal boss fight for the second form. The [[BonusBoss Bonus Bosses]], [[spoiler:HR-D3 and Galacta Knight]], both have very memorable Turning Red sequences. [[spoiler:HR-D3]] in the main Extra story mode is actually a giant Turning Red scenario: [[spoiler:The Egg Engines Boss, Metal General, summons this robot after defeat in Extra Mode. HR-D3]] does not have any Turn Red scenarios in its health bar. [[spoiler:Because it is partially a CallBack to VideoGame/Kirby64TheCrystalShards, meaning it has TWO WHOLE healthbars.]] Then, we have [[spoiler:Galacta Knight]], who is even MORE of a BonusBoss than [[spoiler: HR-D3]], as he isn't even fought in the Extra story mode, but only in [[spoiler:The [[NintendoHard True]] [[BossRush Arena]]]]. He is fought EXACTLY like a normal boss, but instead of his theme from [[spoiler:Kirby Super Star Ultra]] playing, he gets [[spoiler:Landia's theme. Until he actually Turns Red. THEN his own theme music kicks in, he unleashes a combo, and starts using more deadly attacks.]]
* ''VideoGame/IWannaBeTheGuy'' bosses love doing this. Kraidgief and Mecha Birdo are especially notorious for Turning Red, the former first trying to bash you and then throwing fireballs (along with a Kenshiro Spinning Piledriver if he gets too close), and then throws Blankas at you for the final phase; and the latter shooting egg platforms and Shyguys at you for the first phase, firing lasers at you for the second phase, and then going back to the Shyguy phase for the last leg, only the tips of the egg platforms in the last half kill you if you touch them.
** Dracula summons two giant invincible minions that follow you around once he gets damaged enough. These minions turn red themselves and speed up.
* The ''VideoGame/MegaManX'' series tends to like this. Starting from ''Mega Man X2'', you can pretty much expect bosses to do something nastier/cooler if they're more than half down on their health. Possibly another upgrade when they're down to a quarter.
** The BigBad gets bonus points for gradually turning red. And then, there's that boss who turns blue instead.
** ''X8'' takes this even further by giving the bosses a DesperationAttack, during which they are completely invincible. Special notice to the true final boss who will gain a desperation attack that ends the fight in 30 seconds unless you kill him. To do so requires breaking 3 shields and removing the last of his health -- no small feat ordinarily, but doing it without the combo attack is truly impressive.
** The trend to modify bosses' attack patterns once they're down to 1/2 or 1/4th of their hitpoints continues in the sequel series ''VideoGame/MegaManZero''. Special mention goes to the guardians, who not only change patterns, but gain an attack that makes them invincible until they complete it. Moreover, they are covered in flame, which makes it impossible to jump them without climbing a wall, which none of their areas have.
* Pretty much every boss in the ''VideoGame/MegaManBattleNetwork'' series will start attacking more often, upgrade their usual attacks, and/or start using new attacks once their health hits the 50% mark.
* Zakum in ''VideoGame/MapleStory'' goes through this twice. He has three health bars, and his sprite looks more and more damaged as each bar is emptied. The more damaged he is, the more he uses an attack that reduces everyone's HP and MP to 1. When he's down to his last health bar, he uses the attack constantly.
** Papulatus also TurnsRed, although he only does it once. Although the second health bar has very little health and lacks his room-filling magic, he [[FragileSpeedster moves extremely fast]] and flies all over the room. Very deadly considering his CollisionDamage is enough to kill anyone in 1 to 3 hits.
* One of ''VideoGame/FinalFantasyX'''s [[BonusBoss Bonus Bosses]], Neslug, retracts into its shell after losing enough HP, at which point it becomes impervious to any physical attack that isn't an overdrive, and has an irremovable Regen status that will restore craploads of HP, sometimes in the sextuple digits, [[TheComputerIsACheatingBastard never mind that your characters--and pretty much every other enemy--can only restore or inflict up to 99,999 damage with one hit]]. When and if the shell breaks (again, after depleting even more of its HP), Neslug loses its shell and resumes its out-of-shell attacks, only at a faster turn rate.
** There are many bosses who do this in ''VideoGame/FinalFantasyX''. There was [[spoiler:Seymour Flux]], who ushered in the devastating "Total Annihilation" attack after whittling his HP down to 35,000. There was also [[spoiler:Braska's Final Aeon]], who ''pulled a giant sword out of his stomach'' after doing enough damage.
** The penultimate boss [[spoiler:(Seymour Omnis, the form Inside Sin)]] takes this trope literally when it's about to cast [[ThatOneAttack Ultima]] (which could be seen as its "desperation move").
* Many of the already-NintendoHard bosses in ''The VideoGame/HouseOfTheDead'' series will unleash their stronger attacks after losing enough life. For example:
** The Hanged Man becomes more evasive and starts attacking with {{Deadly Lunge}}s.
** The [[GiantSpider Hermit]] does this twice; first it retreats down the pipe and fires web balls at you, then it guards its face until it gets up in your face to attack.
** The Magician employs his hard-to-counter FlashStep attack in his second and fourth phases.
** In ''The House of the Dead 2'', Hierophant starts using its jumping stab attack after losing enough life, and uses this attack exclusively when at critical health.
** The Wheel of Fate in ''The House of the Dead 3'' has three phases: one in which he randomly decides one of three attacks, one in which he throws snowball-like balls of electricity at you, and one in which his health seems to refill completely (though it goes down at the same rate as his cancel gauge) and he shoots sparks to the back of the room that reflect back and, unless shot, will hit you.
** Chariot, the first boss of ''The House of the Dead'', is a subversion. Ordinarily, he is only damageable via a chink in his armor. Hurt him enough, however, and the armor falls off... allowing the players to literally shoot him to pieces.
** The Emperor turns into a floating conglomeration of spheres and his weak point becomes much more difficult to hit. His HOD4 counterpart, The World, has '''two''' desperation attacks, one for each phase, both of them used only when his health is down to 15% or less. In his first form, his desperation attack consists of him creating four ice crystals into the sky, and after a time any crystals left intact mergers into a larger, sturdier, ''faster'' crystal that goes straight for your face. In his second form (where he ''literally'' TurnsRed), he creates a fast-moving ice dragon that spirals high into the sky then quickly descends and bites you. Have fun with that.
* In ''VideoGame/{{Ristar}}'', most bosses change color multiple times as you damage them, sometimes speeding up gradually as this happens, but the boss of Planet Undertow, a shark that you fight in a water-filled cave, features an interesting twist on this trope. Each time you damage it, it knocks out a plug in the floor of the cave and some of the water drains out, leaving you with a progressively smaller space to fight in.
* In ''VideoGame/NinjaGaiden II'', the giant turtles turn glowing red and constantly rain flaming rocks once they reach 1/2 hp.
* A great number of bosses in ''VideoGame/{{Aquaria}}'' fit this trope to a T. Nautilus Prime ''literally'' turns red and gets faster; Mithala shoots bigger and faster shots; the Sun Worm moves faster and messes with the water level more; and the Sunken City boss gets really, really mad. In fact, this trope is exaggerated: when the bosses go berserk, ''the whole'' '''''screen''''' ''turns red!''
* In ''VideoGame/TheTwistedTalesOfSpikeMcFang'', Felina the first Boss TurnsRed when you have her down to her last sliver of HP. When this happens, she suddenly fully heals herself, moves faster, and gets a new attack.
* The Giant Sandworm in ''VideoGame/TalesOfHearts'' effectively clones itself at 1/4 health by adding its tail to the field. The tail has all the same attacks as the head and shares HP. Later in the game, another boss splits itself twice, once at half health and once at a quarter if memory serves.
* In ''VideoGame/{{Xenosaga}}'' Episode III, as an option you could fight [[spoiler: Omega Universitas]] in a simulation; he's no more powerful than he is in the mandatory confrontation, meaning you could take him down in one turn, but after doing so, he transforms into [[spoiler:Omega Id]] and becomes easily capable of killing any one of your characters in a single attack.
* Certain bosses and [[BossInMookClothing unique monsters]] in ''VideoGame/{{Xenoblade}}'' will start busting out new attacks and/or activate an aura that grants them a substantial boost to their combat abilities when their health starts to dwindle. The latter can be removed by certain artes, while you just have to deal with the former.
* ''VideoGame/KingdomOfLoathing'': all of the bosses in the Hobopolis clan dungeon can "flip out" halfway through the fight. However, players can learn skills that let them calm a flipped out boss down.
* Starting with the 6th installment of the ''VideoGame/{{Touhou}}'' series, most bosses will use one or more Spell Cards, usually when their current health bar is down to less than a half. (Starting with the 7th game, Perfect Cherry Blossom, the portion of the health bar where the boss will activate a Spell Card is in red.) When a boss uses a Spell Card, the background changes, and the boss's portrait is flashed on the screen. Spell Card attacks tend to be harder than regular attacks and usually make the boss's health bar drain much slower. However, defeating a Spell Card attack by draining the red portion of the boss's health bar before time runs out (or simply surviving the countdown, for Spell Cards that make the boss temporarily invincible) without getting hit by a single bullet or using a bomb awards the player a considerable score bonus.
** Some bosses will also do this in the middle of a Spell Card, too. Ran Yakumo's Illusion God "Descent of Izuna Gongen" and Yukari Yakumo's Bounded Field "Boundary of Life and Death" both start out deceptively easy but fire progressively more bullets as the user's health bar decreases, and Suwako Moriya's Scourge Sign "Mishaguji-sama" decreases the pause between waves as Suwako's health bar decreases. Don't think you can just sit there without firing and time out the Spell Card to avoid the boss Turning Red, either - when the timer hits 30 seconds left, the Spell Card automatically goes to its hardest difficulty regardless of remaining health.
** This is actually a common trait of the last spellcard for extra bosses, which get harder as their HP lowers by either doing ''it more strongly'' or in Mokou's case, adding more patterns to avoid. Utsuho also pulls this off, despite just being a final boss.
* Jason in the NES game ''VideoGame/FridayThe13th'' does this. You have to defeat him several times over the course of three days/nights. In the second day he alternates between moving normal and fast, and does a bit more damage than in day one. In the third day he stays fast the entire time and does even more damage than he did on day two.
* [[BonusBoss Baal]] from ''Franchise/{{Disgaea}}'' already has utterly ridiculous stats. However, if you kill off all the mooks in his stage before him, his stats (except for HP) double.
** All of the bosses from the spinoff PlatformGame ''VideoGame/PrinnyCanIReallyBeTheHero'' do this when you whittle them down to 25% HP. Regular enemies do this as you damage them, but their tactics don't change.
* ''VideoGame/{{Fraxy}}'' allows an event to check the HP of the weakpoint. If HP of weakpoint is less than 50%, play (Insert all the nasty attacks here.)
** Some designers make the boss Turn Red more than once, leading to a SequentialBoss (sort of: the boss's multiple forms all have the same health bar). Often involves OneWingedAngel as well.
** And now, there's two new types of bosses that turn red: "HardMode / WhatIf" Bosses and "Death Label" bosses. Hard mode bosses have secret forms/attack patterns that activate after the player does something, such as not dying or shooting the boss's tail. "Death Label" bosses are just the regular boss, just faster, deadlier, and maybe possessing more forms.
* ''VideoGame/{{Klonoa}}:''
** Pretty much ''every'' boss in ''VideoGame/{{Klonoa}} 2: Lunatea's Veil'' goes into this mode, picking up a few new stunts. Then, when you kill the boss, [[MadeOfExplodium it blows up. Several times.]] But ''before'' it explodes, it TurnsRed.
*** Bonus points for the fact that the health meters turn to a garish hot pink when it ''turns red''.
** Also, in ''VideoGame/{{Klonoa}}: Door to Phantomile'' (and its Wiimake), the third boss, Gelg Bolm, TurnsRed when you damage it enough. It becomes a lot faster and aggressive in this state, and the weapon it sends after you (a giant peach... thing) is a lot bigger than the first one it sends out earlier in the fight.
* The last boss of ''VideoGame/DragonQuestIV''/''Dragon Warrior IV'', [[spoiler: Necrosaro]], does this ''seven'' times during the battle. In the original NES version, it's the only enemy sprite in the entire game with animation. After you destroy its arms and head, another face emerges from its torso. As you damage it further, it sprouts new arms, bigger legs, and to top it all off, a second head with three eyes. In the Playstation/DS remake, it has extremely detailed animations for each transformation.
* Hwa Jai from the original ''VideoGame/FatalFury'' literally turns red by chugging down a drink after losing over a quarter of his health. When juiced, he gets faster, stronger, and gains a nasty flying knee move known as the "Rocket."
* ''VideoGame/{{Xenogears}}'' has [[spoiler: Grahf]] doing this for the enemies. He will turn up, boost the current boss' power to oblivion and leaves, to the point where his entrance line seriously annoys or freaks out the player. "Does thou desire the power?"
* In ''[[VideoGame/MarioAndLuigiSuperstarSaga Mario & Luigi: Superstar Saga]]'', the last time Popple attacks you, he teams up with Birdo. If you take Popple out first, Birdo loses it and says "You may have defeated my darling, but [[CatchPhrase that is as far as you go]]!" then literally turns red and begins firing off her exploding eggs in a more random pattern.
* Most opponents in ''VideoGame/PunchOut'' for the NES, and all of them for the Wii version, get more difficult the more times you knock them down.
** Don't Star Punch Soda Popinski unless it's to finish him off. Especially if you have low health. He also does it when he gets up after being knocked down, as well as if you knock the soda bottle out of his hands.
** Bald Bull turns red before unleashing a Bull Charge in the Wii version. The second time you fight him in the NES version, regular punches will not knock him down. Once his energy is low enough, you can only drop him with an uppercut or by punching him during a Bull Charge. If you dodge a charge, he'll keep doing them until one of you knocks the other down. In the Wii version, ''only'' a Star Punch can knock him down after the first time you beat him; that said, if you take him to the brink, you usually get one and can use it to finish the job if you time the punch just right as he comes back to you.
* During the fight with [[spoiler:Belius]] in VideoGame/TalesofVesperia, she ''duplicates herself'' after taking a good chunk of damage, making an already hard boss battle into a controller-smasher. You can at least get rid of the Shadow version of the boss by relighting all the torches in the arena.
** Practically all of the bosses in the game and throughout the series in general start using new attacks as their HP lowers. They also have an unpredictable version of this in the games where they can activate Overlimit, as it temporarily lets them spam their attacks (On top of sometimes enabling the use of new ones), makes them ImmuneToFlinching, and permits the usage of their [[LimitBreak Mystic Arte]] if they have one.
* Every boss in ''VideoGame/LaMulana'' does this. Even [[WarmUpBoss Amphisbaena]] becomes faster once you've racked up some damage on him.
* The last GUILT, [[spoiler:Savato]], that you have to fight in ''TraumaCenter: Under the Knife'' does this after you've separated it once. However, given that the game forces you into The Healing Touch at this point, this could possibly be a subversion.
** Also, in ''Trauma Center: Under the Knife 2'', [[spoiler:Pempti, the mutated version, has two cores, destroying one quite literally causes the other one to turn red and go berserk with relentless attacks on the patient until it, or the patient, is dead]]. As well as this, [[spoiler:Aletheia, the final boss, has one last desperate move when you're almost done, blood vessels around the core flash red at a rate faster than the eye can keep up with, if you haven't got the Healing Touch ready to slow things down to a regular version of cut-all-8-blood-vessels-while-they-are-not-red, then you are screwed]].
* Ace suits in ''DynastyWarriorsGundam'' will receive a reddish/pinkish/purplish glow (depending on the state) glow when they go into rage and receive quite a power up when doing so. Also your own suit will start radiating when your SP gauge is full.
* ''VideoGame/DynastyWarriors'' and ''VideoGame/SamuraiWarriors'' will sometimes have enemy generals, usually ones with unique models (IE, playable characters or at least important [=NPCs=]). When knocked down or in a defensive position, they may glow for a moment and suddenly buff themselves. They will also often glow for a few seconds before unleashing a [[LimitBreak Musou attack.]]
** Dynasty Warriors 5 deserves special mention. On specific levels, specific characters will be tougher than usual (with a [[BattleAura red aura of doom]]). As they take damage they give themselves temporary stat boosts (Doubling their Attack or Defense, for example), with the last buff ending in [[SuperMode Musou Rage]] (Increased damage, attack speed, and super armor to all but the most powerful of attacks). Ignoring them while they have these buffs doesn't always work, either. They'll just get it again shortly after they run out.
* Parodied in ''VideoGame/{{Terranigma}}''. After fighting a HumongousMecha, and getting him down to a single hit, he launches a special attack. This attack is easy to dodge, and barely hurts at all if you are hit. After launching it (and dying), the robot says "that last attack was not very impressive."
* The last boss of ''VideoGame/MadWorld'' does this after you finish his ActionCommand, which lowers his health to half.
* The final boss of ''VideoGame/StreetFighterIV'', Seth, [[IAmNotLeftHanded handicaps himself in the first round]] by not using any of his special moves. If you beat him, he'll flash black on the ground, then stand up, levitate, and shout, "WITNESS MY LIMITLESS POWER!" In the second round, he'll go into total SNKBoss mode.
** In ''VideoGame/StreetFighterIII'', if final boss Gill was defeated with a full Super Bar, he would sometimes '''resurrect himself to full health.'''
* Speaking of SNK bosses, Allen O'Neil (an insult-spewing, machine-gun-toting, [[BaldOfEvil bald]] BadAss who shows up in most of the ''VideoGame/MetalSlug'' games) will turn redder and redder the more lead (or whatever) you pump into him. Then he [[NoOneCouldSurviveThat dies]], says "SeeYouInHell!", and [[UnexplainedRecovery recuperates in time for his next appearance]].
** What's more, the end of mission bosses of the Metal Slug series have a tendency to become more aggressive or use more weapons as they become significantly damaged; for example, the Keesi transport plane of mission 1 in Metal Slug 2 starts off by dropping Arab swordsmen to attack you while not laying a finger on you itself, but as it gets a beating, it instead has two Rebel soldiers unload on you with rockets, and the plane itself will start attempting to incincerate you with its afterburners.
* Gaoh, the boss of ''VideoGame/SamuraiShodown V'', transforms into a hulking armored beast when his POW gauge fills. In this form, he is invincible and spams a lunging headbutt attack until the meter drains and he changes back.
* Quite a few bosses in the ''VideoGame/{{MOTHER}}'' series do this:
** The Carbon Dog from ''VideoGame/EarthBound'' transforms into Diamond Dog after he has taken some damage, gaining a noticeable Defense boost, twice the hit points, a Shield, and an attack that can [[StandardStatusEffects diamondize]] party members.
** [[BonusBoss Lil Miss Marshmallow]] from ''VideoGame/{{Mother 3}}'' literally goes into a Pissy Boss Mode when you do enough damage to her, changing appearance from mildly agitated to downright infuriated, and [[TelescopingRobot revealing her multitude of concealed weapons]].
*** Inverted by the Pig Tank, which after sustaining enough damage, will break down and spend almost all of its time doing nothing, plus its one attack is far weaker then the ones it possessed while functional.
*** When [[HeroicDog Boney]] sniffs the Steel Mechorilla, it claims that it smells "weak against thunder!" Unfortunately, using PK Thunder too many times on the Mechorilla makes it [[OhCrap go berserk]], at which point you're screwed, as it starts spamming an attack that hits the entire party for twice the damage its normal attacks deal.
*** [[spoiler: Miracle Fassad]] undergoes a huge case of this, changing his combat style from spamming status effects to nuking you with Omega level PSI attacks that deal borderline OneHitKill level damage.
* Terra in ''VideoGame/KingdomHeartsII FM+ '' goes off with a nasty limit break style attack when he turns red. And [[{{Whoring}} SPAMS it]].
** Also in ''VideoGame/KingdomHeartsII'' is [[ThatOneBoss Xaldin]], who, once you've knocked off a health bar, begins to use longer combos with a larger range and less recovery time in between, spending about 90% of this time in an invincible green glow unless you use a special command on him.
** Most bosses in the Kingdom Hearts series do this. They do everything from split up into multiple enemies, to cloak themselves in Darkness, to lighting on fire, to increasing their attack rate... you get the idea
* Emperor Sun does a version of this in ''VideoGame/JadeEmpire'' - however, instead of getting pissed, he gets desperate (complete with a cut scene showing his waning powers) and starts switching around his defences faster than before (ensuring the player has to change attack style with EVERY HIT in order to get around his immunities.)
** Additionally, Master Smiling Hawk will magically drain the life of one of his followers when he hits half health, getting a couple of new fighting styles- and all his health back. (But he's not exactly hard to beat anyway!)
* The Gigantic Burner in ''VideoGame/ParasiteEve2'' plays this straight. However, the first phase of the battle is also on a hidden [[TimedMission timer]], which can alter the fate of an NPC.
* Most boss fights in ''[[VideoGame/TheLegendOfZeldaALinkToThePast A Link to the Past]]'' have multiple stages (the boss might become faster and more aggressive after taking a certain amount of damage, or Link might have to kill a group of smaller enemies before he can attack the main boss), but the one which adheres most closely to this trope is the fight against the six Armos Knights[[note]] fought twice, once in the Eastern Palace and once in Ganon's Tower[[/note]]. At first, they jump around the room in fixed patterns, but when you have killed five of them, the last one turns from blue to red and actively tries to stomp Link.
** You know a cucco is pissed off when it does this. In ''[[VideoGame/TheLegendOfZeldaSpiritTracks Spirit Tracks]]'', once a cucco turns red, it summons buddies to peck and claw Link to death. [[VideoGameCrueltyPunishment Don't ask how to do this. You should already know.]]
* In ''VideoGame/Uncharted2AmongThieves'' [[spoiler: Lazarevich]] starts spamming you with grenades when you hurt him enough.
* ''VideoGame/TheLordOfTheRingsOnline'' also does this:
** The wight-lord Vathar heals fully when almost dead, and starts spawning lots of worms.
** Mordirith, who is also undead, heals fully when half dead, and announces that what you were fighting before was just an illusion, then demonstrates a few new tricks.
** The Blind One starts spawning clones of itself, all at full health and hitting just as hard as the original.
* In ''VideoGame/NoMoreHeroes'', every boss becomes more aggressive with depleted health. Some learn new attacks, while others employ new tactics. The first boss from the first game, for example, triplicates himself.
** These "new attacks" are, in a couple of cases ([[WakeUpCallBoss Shinobu]] most comes to mind), unblockable insta-kill attacks which can only be avoided if the player has memorised the pose the boss takes, and knows they have to run away as fast as possible whenever they see this boss doing this.
* In ''VideoGame/FinalFight'', Edi E., the third boss, uses his gun after you reduce him to about half his health. In the arcade version, Rolento, the fourth boss, starts dashing around the arena rapidly and [[MadBomber spamming grenades]] when his health bar gets low.
* In ''VideoGame/GuildWars Factions'', [[BigBad Shiro Tagachi]] will use Meditation of the Reaper, which makes him immune to damage and lasts 30 seconds or until 500 damage has been absorbed. And when it ends, Shiro steals 20 health from each player for every second he was meditating... making it imperative to end the meditation as quickly as possible to avoid a party wipe.
* In ''VideoGame/GuildWars2'' the final battle with Scarlet Briar featured her going through several stages. When her three holograms are destroyed, she flies into a rage and begins powering up her most powerful weapon to wipe out everyone at once.
* Non videogame example: [[Anime/YuGiOh Dark Master Zorc]] does this near the end of the Monster World arc after Yugi separates Bakura from the Spirit of the Ring.
* The Conqueror, the BigBad of ''VideoGame/TheLastRemnant'', literally [[BattleAura turns red]] after you get his HP halfway down.
* Every boss in ''VideoGame/AnUntitledStory'' is like this. The [=StoneCastle=] face boss literally turns red as well.
* Pretty much every boss in the video game adaptation of ''VideoGame/ScottPilgrimVsTheWorld'' start flashing gold once their health has been depleted past a certain point-- mimicking the players' own Hyper Mode. They then get much faster and start spamming their strongest attacks.
* All bosses in the NES ''VideoGame/AdventureIsland'' series literally [[ExactlyWhatItSaysOnTheTin turn red]], but are not actually all that much harder afterwards. Usually it will just switch from one projectile per turn to two. So more than anything, [[ColourCodedForYourConvenience it's just a sign that you're about to kill it]].
* Killian's [[CoolPlane jump jet]] in ''VideoGame/PerfectDark Zero'' starts [[WeaponizedExhaust burning you with its engine flames]](which takes off at least half your health and ignore armor) once you've damaged it significantly, as well as launching missiles more often. And when you beat it, [[TakingYouWithMe it tries to take you down with it]].
* Hibachi in the ''VideoGame/DoDonPachi'' series. The initial BulletHell assault is bad enough, then it becomes a monster [[NightmareFuel that nightmares are made of]].
** Many BulletHell shooters such as the above have evolving bosses. One unique example is ''ESP. Ra De'' (from Cave, the same company that made ''[[VideoGame/DonPachi DoDonpachi]]''). There were two types of bosses: mechs and ESPers. Mechs "turned red" in pretty standard fashion like most shooters of the type. ESPers were worse: they buffed significantly ''multiple times''. They had multiple life gauges, and each one you emptied out turned them "redder" and "redder".
** If you beat Golden Disaster with Strong Style without dying, you face Zatsuza, an [[SerialEscalation even tougher]] literal red version of Hibachi. This "Zatsuza" can be easily identified with the [[NightmareFuel nightmarish]] [[http://www.youtube.com/watch?v=MY9LTWjcvq0 music in the background]] once you meet this monster.
* The BonusBoss of ''VideoGame/EtrianOdyssey 3: The Drowned City''. It starts as a massive, screen-hogging EldritchAbomination, which only turns out to be its ''bottom half''. And midway in the fight against its top part, it suddenly ''flares up'' with a roar, changes shape, and starts the next phase of the fight with ''plenty'' of beatings which can easily one-shot your entire party if you're unlucky.
* The ''VideoGame/{{Gradius}}'' games have several examples, such as Big Core MK III, which rapid-fire {{Beam Spam}}s you after you destroy two of its cores, and the [[ExactlyWhatItSaysOnTheTin Berserk Core]].
* Sou-Banchou in ''Franchise/TokimekiMemorial 1'' and ''2''. After you've depleted his health to around half of it, he throws away / [[ClothingDamage tears up]] [[Manga/FistOfTheNorthStar Kenshiro]]-style his upper coat (depending on the game) and [[AttackOfTheFiftyFootWhatever becomes giant]]. Upon this transformation, he gains extremely powerful attacks, and in ''Tokimeki Memorial 2'', a PowerNullifier ability that negates your LimitBreak if you have one.
* The Lion Keeper in ''Karnov''. Kill the keeper first, and the lion goes berserk. Kill the lion first, and the keeper throws a stream of knives.
* Most bosses in the ''VideoGame/TimeCrisis'' series have multiple shades of red.
* Several ''VideoGame/{{Ikaruga}}'' bosses. The third boss spins faster and fires [[WaveMotionGun wave motion cannons]], the fourth boss also activates a laser after you destroy the hatches guarding its core, and Tageri's third form has its {{beam spam}}s become faster and its BulletHell denser as you damage it.
* Many bosses in ''VideoGame/TheGuardianLegend'':
** [[ThatOneBoss Grimgrin]]. When you get his health down significantly, he turns orange and starts churning out projectiles like crazy, creating somewhat of a BulletHell situation.
** When Clawbot takes enough damage, the claws first turn red and then detach from the base, which starts firing its laser more rapidly.
* Many ''VideoGame/{{Raiden}}'' bosses. Some, such as the BaseOnWheels boss in the first game, up their firepower when you destroy their optional parts. In the fourth game, several of the bosses turn red multiple times. ''Raiden II'''s fifth boss (ThatOneBoss to many players) literally turns red in its third form.
* All bosses in ''VideoGame/RayCrisis'' have variable shades of red depending on the order in which the stages are played.
* Bosses in ''VideoGame/{{Zanac}}'' turn red [[StalkedByTheBell if the fight drags on too long]].
* In ''VideoGame/{{Halo 2}}'', each time you score a hit on the Heretic Leader, he retreats into the ventilation ducts, then comes back with a larger number of {{attack drone}}s.
* In ''Roleplay/MSFHighForum'', Kim does this when she's hit in a game of dodgeball. The effect? Twice as powerful as before.
* ''VideoGame/DragonAgeOrigins'' has numerous examples, including the Broodmother (who's a real pushover until turning red and summoning lots of mooks) and [[spoiler: the Archdemon, who also summons mooks after getting down to about half health]].
** Special mention has to go to the Sloth Demon that [[spoiler: traps your party in the Fade in the Circle Tower (''Broken Circle'' part of the main quest)]]. Uses an especially annoying variation of the trope as he assumes a new form when brought to near 0 HP, each with progressively deadlier abilities - and fully regenerated health. [[spoiler: And he does this ''four'' times.]]
* Most bosses in ''VideoGame/BlasterMaster'', particularly Stage 3 (speeds up) and Stage 5 (fires ever-denser bubble spams).
* Popular in the ''VideoGame/{{Rayman}}'' series:
** In [[VideoGame/{{Rayman1995}} the original game]], Mr. Dark starts turning into some of the previous bosses mashed together as he gets lower on health.
** ''VideoGame/{{Rayman 2}}'' has you punching bombs back at the Golgroth, the final boss. Then the roof falls in and you have to fly around shooting it into lava, whilst missiles chase you and said lava rises. Frustrating is an understatement.
** In ''VideoGame/Rayman3HoodlumHavoc'', the final boss is incredibly hard to fight at the start. He then destroys half the arena, and things just start getting worse from there....
* Abyss from ''VideoGame/MarvelVsCapcom2'' shows his true powers once you destroy his armor, then turns into a literal red demon after you beat the second phase.
* ''VideoGame/TheWorldEndsWithYou'':
** Sho Minamimoto does this after about 1/3 of his health is gone, gaining quicker attacks and permanently staying in his noise form for the rest of the battle.
** Vespertillo Canor (the second giant bat) turns into a single golden bat similar to the one Beat and Rhyme defeated a while back. It can only attack you once on each screen for each time it pops up, and has almost no health.
* ''VideoGame/WhiteKnightChronicles''. Every boss. Every single boss has an enrage mode where they turn red and do far more damage after you dare to hit them a few times. Because this is based on how many times you damaged them and not their overall health they can enrage multiple times in one fight, making them some of the pissiest bosses in any game ever. To add to the effect many bosses will throw visible tantrums when entering enrage mode.
* The ''Franchise/SilentHill'' series does this a number of times. For example, in ''VideoGame/SilentHill1'', the Split-Head utilizes its OneHitKill vertical jaws after you blast it a few times with the shotgun, and the God in ''VideoGame/SilentHill3'' throws faster and deadlier fire waves when its HP is low.
* In ''VideoGame/AlphaProtocol'', Brayko takes cocaine once you get his health down to 50% (and after that as a regular part of his attack pattern), which temporarily turns him into a knife-swinging, immune-to-stun-and-knockdown madman (well, moreso than usual) who runs supernaturally fast and will hunt you down and shank you. He turns into a subversion if you have Steven Heck on your contact list, as he will spike Brayko's drug stash which means Brayko doesn't get the speed bonuses and damages himself slightly every time he does it.
** Similarly, if you kill his bodyguards Conrad Marburg [[BerserkButton will flip out]] and hunt you down for a good round of fistcuffs until you damage him sufficiently again. Despite being a 50-year old man using his bare hands, he's almost as nasty as Brayko in melee.
* In ''PN03'', Loewenzahn partially transforms from a insectoid tank into a pterosaur-on-wheels when down to about 1/3 HP, and goes fully OneWingedAngel as a robotic phoenix for the last part of the rematch battle. This last form is a [[ClippedWingAngel pushover]], however. [[FinalBoss Alraune]] starts shooting paralyzing homing plasma bolts at 1/2 HP, and employs its [[WaveMotionGun death laser]] BeamSpam when it's down to 1/4 HP.
* In ''VideoGame/GodsEaterBurst'', Hannibal (and its more powerful variant Corrosive Hannibal) gains access to a new attack where it levitates and hits you repeatedly with pillars of fire when you break the scale on its back. Much truer to this trope, the Arda Nova (and its stronger variant) becomes much faster and gains access to a completely different moveset if (and it's difficult not to) you take down its male half first.
* Most bosses in ''VideoGame/{{Vanquish}}''. The first boss fires off an intense MacrossMissileMassacre just before it [[TransformingMecha transforms]] from SpiderTank to {{beam spam}}ming HumongousMecha, then spams more missiles when that form's HP is depleted about halfway.
* Boss battles in ''[[VideoGame/GundemoniumSeries Hitogata Happa]]'' are timed, and if the boss is not defeated when the time expires, it goes into "Error Mode", significantly increasing its attack speed. In addition, you only get one shot to destroy the boss while it's in Error Mode. Die even once (except for sacrificing your dolls as {{Action Bomb}}s), and it's GameOver.
* [[EvilTwin Sabata]] does this in ''VideoGame/{{Boktai}}''. Once you empty his life-bar he replenishes all his health, knocks out the lights, and gains a couple new attacks.
** In Boktai 3, he does this a solid ''five times'' during the fight. Each time you deplete a fifth of his health, his attack pattern changes completely and he gets more powerful.
* The large Oni[[labelnote:*]]bosses or subbosses[[/labelnote]] of ''VideoGame/{{Toukiden}}'' become "enraged" after taking a lot of damage or losing a limb. In this state, they gain glowing red eyes and a purple sheen. They may also transform when near death; both states are more aggressive than normal and may have special attacks.
* The larger Aragami[[labelnote:*]]Minibosses, at least[[/labelnote]] of ''VideoGame/GodEaterBurst'' can go berserk after taking enough damage. They become faster, more aggressive, and may use special attacks.
* In ''VideoGame/AngryVideoGameNerdAdventures'', Skylar, AKA the "Where did YOU learn to fly?" bitch from ''Cybermorph'', literally turns red and goes berserk after you destroy her OrbitingParticleShield of "children". The {{final boss}}, Fred Fuchs, goes from throwing sinusoidally-traveling fireballs, to divebombing you with a pair of [[EpicFlail balls & chains]], to [[DungFu defecating a literal shit storm]], to swinging two additional long-chained flails.
* ''VideoGame/DoubleDragonNeon'''s [[TrueFinalBoss Giga Skullmageddon]] becomes increasingly faster and agressive as his HP wears down. In his final phase, he literally glows red in addition to [[EpilepticFlashingLights epileptically flashing orange]], and has an inescapable instant-kill hyper combo attack.
* Several [[ThatOneBoss Those Ones Bosses ]] from ''VideoGame/DarkSoulsII'' do this:
** Both Smelter Demons have two stages of this. First, at 90-80% health, the demon will intensify the flames within its body, burning any player close enough (the first one gets bonus points by literally turning red from the flames). Then, at 60% health, it will thrust its sword into those flames, [[FlamingSword igniting it]] as well. Worse still, those buffs also have a backup timer triggers, so it's possible to have flaming demon with a flaming sword without actually managing to hit him once.
** Raime the Fume Knight starts dual-wielding his signature Fume swords, normal sword in right hand and [[{{BFS}} gargantuan Ultra Greatsword]] [[OneHandedZweihander in left hand]]. He's very agressive, but his attacks are easy dodgeable. However, at some yet undetermined point in the battle he'll ditch the smaller sword, take the BFS in two hands and ''light it on black fire''. From now on, not only his attacks become terrifyingly fast and and sword starts dealing Physical, Fire and Dark damage at the same time, but he gains the ablity to swipe half of the arena with extremely damaging attacks, either a circular motion of an extended FlamingSword of a bunch of fireballs spiraling out from him. As a cherry on the top, enter the arena wearing specific armor ([[spoiler: namely, Raime's friend turned enemy Velstadt's helmet]]) and he will TurnRed ''immediately at the start''.
** In the battle with Lud and Zallen, the King's Pets, Lud will fight you while Zallen watches from the top of the wall. Once Lud loses some health (actual amount depends on how many summoned phantoms you have with you), Zallen will join the skirmish. Also, [[KillOneOthersGetStronger killing either one of them]] will make other one [[RoaringRampageOfRevenge enraged]] and temporarily buff himself up (including RegeneratingHealth).
* ''VideoGame/{{Bloodborne}}'' has Lady Maria who is a competent boss with a nice moveset and a lot of speed. Once you get her to about half her health she stabs herself and uses her blood to increase the range of her hits, a la ''VideoGame/{{God of War}}''. Get her to about a fourth of her health and she does it again, increasing her range further and causing the blood to burst into flames, causing a lot of extra elemental damage. In this game the fact that she doesn't use this behavior from the start is justified in that she, and other hunters, use their own blood to power up, and stabbing yourself should probably be a last resort.
* In ''AngryBirdsEpic'', Wizpig transforms into Demonic Wizpig in the final level (before Chronicle Caves) after the player defeats him in the first round.
* In ''VideoGame/{{Terraria}}'', most bosses tend to take their second form after having been reduced to half health: Eye of Cthulhu loses a part, and the eyeball [[BodyHorror transforms into a giant jaw]], the Twins start using more powerful attacks, the Eater of World gets split into multiple worms, and the final [[spoiler:pre-Hardmode]] boss releases increasingly rapid laser flurries. In [[spoiler:Hardmode]], [[spoiler:Plantera]] is a sheer nightmare after she is brought down to half health, trying to maul you with her body, and if you leave the Underground Jungle hoping to escape, she will get enraged and will try to charge at you at a ludicrous speed while inflicting increased damage... isn't that enough?
* ''VideoGame/AVeryLongRopeToTheTopOfTheSky'':
** Weiss will activate an overdrive chip at low health, boosting his stats.
** In the third fight against [[spoiler:Rutger]], he'll go OneWingedAngel after taking some damage, giving him a slew of new attacks.
** The {{Bonus Boss}}es love this:
*** The Mother will gain two actions per round -- "[[BossBanter Do not think I am weak!]]" Indeed, most players will probably think she was quite easy up to that point.
*** The second Phobos will [[WolfpackBoss summon two clones to help him out]] when he reaches half health, along with the quip, "You're already barely holding on... What hope do you have?"
*** God and the Eater each get ''three'' powerups. God will summon one [[FlunkyBoss flunky]], then two, then get a stat boost ("I'll show you the power of your creator!"). The Eater will get two actions per round ("You think you've hurt me? This is only the beginning!"), then three ("You may be strong, but I'll strip your skin and add you to the bone pile!"), then a stat boost (without a quip, oddly).
*** The [[spoiler:Rutger]] in the expert arena gets a stat boost after taking some damage.
* Hans Volter in ''VideoGame/KillingFloor2'' has this in four stages shown by the light on his chest along with various wires on his body. At first he is adorned in a faint, gentle green glow, followed by a noticeably brighter yellow. Later on these become orange along with his mechanical parts sparking, finally ending with chest light and wires shining a vicious red illuminating him and his surroundings brightly while electrical zaps spark all over him. He also heavily lampshades, if not blatantly explains these stages by losing his usual cheeky taunting; growing increasingly angry and with quotes at the start of each later stage. On top of all this in his final stage he employs [[DesperationAttack desperation attacks]], putting aside his usual tactics of splitting up the team, throwing smoke bomb-like gas grenades causing area of denial and blindness, stalking those who split from the group and using his rifles at range in favor of rushing the closest player and mauling them in long frenzied combos. As well as throwing explosive and corrosive gas grenades absolutely everywhere in all directions, even if those will hurt him more than it does the players, screaming "''Die die die!''" and the like.
--> Stage 2 "Fools! That was the easy part! Now prepare to face new attacks!"
--> Stage 3 "Really? You are making me step up the attacks, again?
--> Stage 4 "NOOO! You cannot still be here! No! Nien! This! Will! Not! Do! I will use EVERYTHING! FACE EVERYTHING, SCUM! EVERYTHING!"
* The bosses in the platformer action adventure ''VideoGame/MystikBelle''. Bonus points for literally turning more and more red as the fight goes on!
[[/folder]]

[[folder:Subversions and Inversions]]
* The [[CyberNinja cyborg ninja]] from the first ''VideoGame/MetalGearSolid'' was incredibly impressive in combat up until you depleted most of his health, at which point he stuck to one feinting punch attack while crying desperately, [[DoesThisRemindYouOfAnything "That's it! Hurt me more! More! More!"]]
** The BB Corps members in ''VideoGame/MetalGearSolid4'' are formidable in their suits, but when the suit is broken their only attack is to hobble around slowly, [[JigglePhysics bouncing]], [[FanDisservice making creepy ambient noise]] and [[DysfunctionJunction preying on Snake's epic-level intimacy issues]]. And also exploding if they grabbed you.
** In ''VideoGame/MetalGearRisingRevengeance'', Raiden glows red when "[[SuperpoweredEvilSide Jack the Ripper]]" emerges. This first occurs when he's pushed too far by Sam and Monsoon's tauntings, and thereafter works as a SuperMode for Raiden in gameplay.
* Most of the [[TheFederation GUN]] bosses from the ''Franchise/SonicTheHedgehog'' franchise tend to get weaker when they get damaged. There are exceptions to this though.
* Injury causes the main character to transform into an invincible, superpowered (and red) dragon during a boss fight in ''BreathOfFire: Dragon Quarter''.
* A few of the big bosses in ''VideoGame/CityOfHeroes'' invert this trope, although probably not intentionally. Diabolique would be the most memorable, as her new ability at low health is to pop up a force field bubble that prevents her from attacking or being attacked, giving players a nice breather to regain endurance and health at the cost of being a little irritating. Marauder and Bobcat have a more conventional glow power that reduces incoming damage at low health while still letting them attack. That'd be a conventional use of the trope, except that they lack long-range attacks, and when the glow wears off in three minutes, the power's crash means they'd end up with less health than before they used the power.
** Romulus, on the other hand, comes back to life no less then three times. And every rebirth brings reinforcements and a nice healthy serving of stun. Not sure if he himself actually gets any more powerful, though.
** Romulus eats one of his [[spoiler: Nictus helpers]] every time he resurrects, taking their special power out of the fight and making things easier.
* [[spoiler:Ed the Undying]] in ''VideoGame/KingdomOfLoathing''. He fights you no less than seven times in a row (the game won't let you enter his chamber unless you have at least seven adventures to spare.) He gets more and more beat up with each fight--each form has less health than the one before, to the point where you can easily beat the sixth and seventh in about one or two hits depending on level, and each form's portrait shows him in worse and worse condition. Eventually his unwillingness to give up despite how badly he's been beaten approaches levels reminiscent of the Black Knight scene from Monty Python and the Holy Grail. The pre-battle narration for his fifth form even includes the dialogue "C'mon, dude. This is ridiculous." "[[spoiler:UNDYING!]]" "''sigh.''"
** However, though his HitPoints are halved each fight, his attack power does not change. And you can't heal between battles. Fortunately, your familiar effect still has a normal chance of going off - including those that heal you after battles.
** Eventually you just [[CrowningMomentOfFunny sweep his remains into the corner]] and claim victory.
** The [[BigBad Naughty Sorceress]] plays this both ways - she has three forms; the second is stronger than the first, but the third is [[spoiler: a literal one hit kill if you have the right item in your inventory. And a one hit kill for ''you'' if you don't]].
* [[spoiler:Gilgamesh]] in ''VideoGame/FinalFantasyV'', when you fight at Exdeath's/X-death's castle halfway through his health he transforms into a more menacing form, wielding what he believes to be the ultimate sword, Excalibur. But in reality the sword is the fake, [[JokeItem significantly underpowered Excalipoor]], causing very little damage. Then he is [[YouHaveFailedMe banished to another dimension]]. Instant win.
* In ''VideoGame/TheLegendOfZeldaTwilightPrincess'', Armogohma makes a comeback after you've seemingly defeated it. However, this "second form" just consists of a group of small spiders carrying its eye around, trying to escape you.
* In ''VideoGame/{{Pikmin}} 2'', the Waterwraith, a humanoid blob of water attached to steamroller-like wheels, does this when you finally get a fair battle against it. When its health hits zero the wheels explode into dust and the "Boss Defeated" music begins to play, but then cuts itself off and flows into an eerie-yet-comical version of the boss theme while the Waterwraith, alive but disarmed, begins panicking and running around the arena, trying to get away from you. It can't even hurt you at this point, and chasing it down and killing it is [[ImplacableMan highly]] [[StalkedByTheBell satis]][[ParanoiaFuel fying]].
* All of the bosses in ''VideoGame/ArdyLightfoot'' (except Beecroft) do this, though only as an indication that they're one hit point away from defeat. The most ridiculous example by far is the FinalBoss, Visconti. After dealing with the apparent final blow while he is red, he suddenly turns blue and changes the strategy of the fight. Dealing enough damage to him in this form turns him back to red, though when you hit him like this this time, he turns grey and changes tactics ''again''! It's not until you hit him when he's red for the ''third time'' when he's KilledOffForReal.
* ''VideoGame/PrincessTomatoInTheSaladKingdom'' does this in an AdventureGame, with the appropriately named [[Music/TheBeatles Sgt. Pepper]] (he goes from green to red).
* {{Inverted|Trope}} in the NES version of ''Bubble Bobble '''Part''' 2'': In the ([[NintendoHard really hard]]) [[BonusStage bonus games]] which would otherwise be an UnexpectedGameplayChange, whoever loses the point to his opponent turns red.
* In the indie game ''VideoGame/BattleshipsForever'', ships go gradually weaker when armor plates, modules and gun turrets are chipped while not upgrading their remaining ones, sometimes resulting ships unable to attack the opponent after all.
** The game it was based on, ''VideoGame/WarningForever'', didn't behave the same. Some otherwise empty sections (including the core) would fire bullets in a spread pattern if nothing is attached to them.
* Every boss in ''VideoGame/BigBangMini''.
* Bosses in ''Manga/OnePiece: Unlimited Adventure'' do this, but [[PsychoElectro Eneru]] takes this a step further: after his HP is depleted, he restarts his heart (something he does in the original series), making you fight him [[HeadsIWinTailsYouLose all over again]] this time with more bolts of lightning falling from the sky.
** Rob Lucci does pretty much the same thing he did in series. After beating down his unassuming-looking human form, he uses the Cat-Cat Fruit (Model Leopard) and turns into a super-dangerous leopard-man.
* In ''[=rRootage=]'', once you reduce a boss's HP to a specified amount on its life meter, it will get stunned for a few seconds, then take on a second form with different, often more difficult attacks.
* Abigail from the first ''VideoGame/FinalFight'' would occasionally turn red and charge at the player with a running punch, roaring as he powers it up. Subversion seeing as this charge is actually easier to stop than some of his others where he retains his normal skin colour and goes for a grab or a tackle instead..
* Dracula in ''VideoGame/IWannaBeTheGuy'' parodies this. Normally when he shouts "Behold my true form and despair!", he becomes a hulking behemoth of a final boss. In this, he becomes [[spoiler: A Waddle-Doo that can be taken out with one shot.]]
* Although technically not in the same boss battle, [[spoiler:Darth Vader]] in ''VideoGame/TheForceUnleashed'' becomes excessively more aggressive and powerful once his armour has been severely damaged [[spoiler:including the life support helmet the removal of which hastened his death in ''Return of the Jedi'']].
* Every boss in ''VideoGame/MuramasaTheDemonBlade'' does this multiple times, partially because they can [[DamageSpongeBoss soak up a LOT of damage]] before being defeated. Each time you knock a boss' primary health bar down to zero, it gets angrier and its attack pattern changes.
** A weird example is [[AttackOfThe50FootWhatever Ippondatara]]: You start with fighting his foot from the sky, then after a while you're carried up where you're confronted with his torso (which has more dangerous attacks). However during this phase you can turn him in the harmless [[FullBoarAction Inosasao]] and deal a lot of damage to him.
* In ''VideoGame/{{Tomba}} 2'', after you throw a evil pig into the pig bag at least two times, they lose their staff and do a different attack.
* In ''VideoGame/WorldOfWarcraft'' when fighting Arthas when he gets down to about 5% health he kills the entire raid in one move. Except that then everyone is resurrected and gets to wail on Arthas while he's held defenseless.
* When [[BigBad Nihilanth]] from ''VideoGame/HalfLife1'' is fully powered and healthy, it can either send a homing teleporter orb that summons some mooks into the battle and will teleport you into the SealedRoomInTheMiddleOfNowhere if it cathes you, or unleash a devastating bunch of ball-lightnings which can obliterate you and are hard to dodge, even though the player character can strafe at a speed approximately three times faster than a normal human's sprint. But, when you drain its energy and health, it opens its head, starts to moan and now can only fire a single pathetic ball-lightning at time, making it easier to get to its brain.
* Two bosses in ''VideoGame/{{Tyrian}}'' implement this. The first boss plays this as mixed, where its armaments are destroyed but it still has an EmergencyWeapon. The Savara V's boss has all its armaments destroyed . when low on health, making it impossible for him to attack you. (You can still die if you push yourself into him.)
* ''VideoGame/RakenzarnTales'' normally plays it straight, but amusingly inverts it when you first fight Samuel. He's weaker than the bosses of the last few chapters and once half his HP is gone, he becomes demoralized and loses defense points.

[[/folder]]

[[folder:Other]]
* In ''TabletopGame/DungeonsAndDragons'' 4e, all creatures have a "Bloodied" threshold, normally equal to half the creature's normal maximum HP. For many creatures this means little. For others, they will gain new attacks, a powerup, or special attribute modifiers when they hit this. However, others will become LESS powerful, losing auras or switching to substandard attacks. Also, some [=PCs=] have such abilities, and some powers from both sides can cause extra pain to creatures that are already bloodied.
** The same applies in reverse, too: Monsters can do nasty things to Bloodied players, but Bloodied players can [[TurnsRed Turn Red]] in various ways themselves.
** In the 4th edition, players who choose the right powers can become more powerful after taking enough damage to become "bloodied".
* In ''VideoGame/DwarfFortress'', any animal or demihuman can become "enraged" when facing insurmountable odds, especially after serious damage to self and nearby allies.
* A number of the evilities in the ''Franchise/{{Disgaea}}'' series activate either when a character is in critical health or when allies are defeated, granting benefits like increased attack power or evasion, or immunity to certain attack types. The most powerful of them is One-Man Army, which doubles a character's stats if they're the last one alive on their side, which can make them extremely difficult, if not impossible to kill depending how high their stats were to begin with.
** This can be (intentionally) exploited by equipping a character with a "Dumbbell", which sets the character's max HP to 25% of normal, keeping them in Critical HP -- and, therefore, Turned Red -- for the entire fight. One-Man army requires that the other 9 guys on your team be dead first, so you can just bring along 9 cheap, disposable units to use for that purpose (such as lv1 prinnies, who can all be taken out in a single turn and resurrected later for pocket change)...If a character has a "Critical HP" Evility with a Dumbbell, AND One-Man Army, they can be quite the ''GameBreaker''. One can also use gear/Evilities that increase stats based on how many allies have died for a similar effect.
* ''Franchise/FatalFrame'' allows bosses ''and'' certain regular ghosts to do this in the various games. In ''Fatal Frame II'', it's called Dark Return and the ghost glows with a purple aura, recovers half of their health and becomes much faster and stronger. ''Fatal Frame IV'' has them 'bloom', causing their faces to become distorted, which makes them stronger and more difficult for the filament at the top to spot them immediately.
* ''[[VideoGame/PunchOut Super Punch-Out!!]]'': Narcis Prince is a [[TheFightingNarcissist vain]] British boxer who fights very defensively. Punching him in the face angers him, making him fight more aggressively (and his punches cause more damage). But he fights carelessly, leaving himself open for more punishment.
* ''VideoGame/DragonFable'' has a few normal enemies that get noticeably stronger when they drop below a certain amount of health; the best example is the undead berserkers, which ''literally'' turn red. The boss fight against Greed will involve Greed getting pissy and killing you if you let the fight drag out for too many turns, and the HopelessBossFight against [[spoiler: a newly [[ScaledUp dragon-fied]] Drakath]] is still UnwinnableByDesign even if you've managed to whittle his health down to around 8,000 or below because he TurnsRed.
* ''VideoGame/CopyKitty'': Boki's ability is to ''copy the opponent's powers'', so on the occasions that the boss TurnsRed, Boki will copy that power boost and gain additional power herself. Defeating one boss even hinges on this: its shields are powerful enough to block most attacks, making scoring a hit very difficult: so trick it into powering up. When it does this, the power Boki copies off of it is enough to shatter the shields after a few attacks.
* From the Onion: [[http://www.theonion.com/articles/update-giant-bin-laden-destroys-new-york-washingto,20536/ UPDATE: Giant Bin Laden Destroys New York, Washington]].
* The Dark Ascension expansion in ''TabletopGame/MagicTheGathering'' introduces a new ability called Fateful Hour. Cards with this ability become more powerful than normal provided you have less than five life.
** The Innistrad block features Undying. When a creature with Undying dies, it returns to the battlefield with a +1/+1 counter on it (i.e. stronger), provided it didn't already have one, otherwise it dies for real.
** The card [[http://magiccards.info/8e/en/250.html Fungusaur]] (and [[http://magiccards.info/pds/en/21.html Fungus Sliver]] as well as others) become more powerful the more damage they're dealt. Note that damage is removed at the end of each turn, but they get to keep their redness.
* Being set in an MMORPG, the anime ''LightNovel/SwordArtOnline'' also features this trope. In "Aria in the Starless Night", when Illfang the Kobold Lord's HP hit 25% (15% in the anime) it was designed to toss its axe and shield aside and gain a completely different attack pattern by unsheathing its talwar...[[spoiler:which was changed to a katana in the full release of SAO, which [[OhCrap caused radical changes to its movement speed and skill-chaining capability.]]]]
* ''Roleplay/DestroyTheGodmodder'': The Godmodder increases in power as he takes more damage, to the point where only special game-breaking events can damage him properly.
[[/folder]]

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