->"''That which does not kill me can only make me stronger.''"
-->-- '''Creator/FriedrichNietzsche'''

->"''It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is the most adaptable to change.''"
-->-- '''Main/CharlesDarwin'''

This is an enemy whose power is to [[EvolutionPowerUp adapt]] to any power used against it.

Hit it with a fireball? Next time it's immune to fire. Same with any ElementalRockPaperScissors attack. Cut it, it now has armor. Psychic powers, it now has mindshields.

Logic would dictate the "easy" way to beat it is to use an overwhelming attack to begin with. However, this goes against most heroic codes, so by the time they've slowly cranked up the power of their attacks, the villain has "adapted" quite a bit.

Beings with an Adaptive Ability are very often [[TheSocialDarwinist Social Darwinists]], if they're not mindless monsters. When combined with a sufficient HealingFactor, it can effectively make them [[NighInvulnerability invincible]].

The result is ItOnlyWorksOnce. The good guys will easily be convinced the EvilEvolves. The functional opposite is PowerCopying. A sub-trope of FeedItWithFire. Compare and contrast with EnergyAbsorption, where the defender is actually ''powered'' by being attacked. See also AdaptiveArmor.

They have a high chance of being an UltimateLifeForm.

----
!!Examples

[[foldercontrol]]

[[folder:Anime and Manga]]
* In ''Manga/JoJosBizarreAdventure'', the Big Bad from Part 2, Cars, uses the Red Jewel of Asia to instantly become the ultimate creature, with all of earth's evolution in hand and the ability to adapt to any attack. He was effectively immune to every possible attack because he could simply change into a form that resisted it before it even hit him. Even when thrown into a volcano he surrounded his body with bags of air to insulate him from the immense heat. He was defeated by being shot into space by the volcano to float around forever until he eventually ceased thinking, effectively making him dead.
* Kuro Momotaro from ''Manga/YuYuHakusho''. His body possesses the ability to memorize the damage of any attack that hits him, while his weapons, the Steaming Spheres heal him from that damage, and give him the power to overcome it. [[LoopholeAbuse Probably a useless ability if he's]] [[OneHitKill killed in one shot]] though.
* Many of the enemies in ''Manga/SaintSeiya'' are fond of declaring that they could not be hit by a technique once they have already seen it. Given our heroes' reliance on StockFootage {{finishing move}}s, this seems like it would be a downright crippling handicap for them ...
* Shishioh from ''Manga/RurouniKenshin'' has a non-supernatural version of this. One of his skills is that he just innately knows how to counter any attack he sees once.
* Anyone with Saiyan blood from Franchise/{{Dragonball}} receive large increases in strength upon recovering from near-fatal injuries. The ability is known as Zenkai.
** The Saiyans are the embodiment of the Nietzsche's famous quote. If they are near-death for whatever reason, when they are recovered, they will come back stronger. A few enemies were too powerful for this to matter much though.
*** The Dragon Ball Z RPG for the SNES had this implemented: If a Saiyan character won a battle with 5 or less HP remaining, they would gain a level immediately no matter what.
** Since Cell was partially cloned from Saiyan cells, he has this ability as well. In fact, the combined abilities to Self-Destruct + Survive so long as one cell remains + come back stronger from a near-death experience is quite dangerous.
** ''The Return of Cooler'', anyone? The entire point in that sequel to Cooler's Revenge is that just as Cooler's body was being destroyed, his mind merged with a sentient super-computer/space-ship. The ship rebuilds him as a mechanical lifeform, and now, thanks to the ship's enormous resources, whenever Cooler's body is damaged, the ship simply repairs his body or fabricates a new one with whatever vulnerabilities it learned about removed.
*** This comes to a head when the computer decides Cooler's main flaw is that there's only one of him. Cue enormous army of Cooler robo-clones.
* The [[EldritchAbomination D-Reaper]] of ''Anime/DigimonTamers'' showed an impressive capability for evolution (then again, it operated like a quantum computer); Originally, it ''just'' killed by touching. Then it developed "agents", foot soldiers who kept damaging attacks away from it. These agents then got more and more specialised; some were gunners, others anti-air units, others were scouts, melee fighters, defense specialists, etc. Upon a debilitating EMP attack, it then integrated all of these capabilities into one massive being and overwhelmed the signal. Ultimately, it was considered to be invincible so the only way they could deal with it was to [[spoiler: turn back ''time'' to regress it to a more primitive state, which means that it remained very much alive.]]
* The Evolutionary Invasion Objects in ''{{Nobunagun}}'' rapidly create new species based on their experiences from past battles. After Nobunagun shoots down a whole battalion of them, the next one they fight has tough armor that her bullets can't penetrate.
* In ''Manga/MagicKnightRayearth,'' the monster Atalante can do this. (What happens when you decide that overwhelming force is the way to go... ''after'' you've let it adapt way too much already? [[OhCrap Very bad things]].)
* One villain in one ''TenchiMuyo'' manga series had this power. Luckily for Tenchi, it turns out that Lighthawk Wings were much too powerful to copy.
* Taken to an annoying degree with Naraku from ''Manga/InuYasha''. He rarely shows up, preferring to attack through subordinates, but when he does, he's always too powerful to take down with whatever attack was effective against him last time. One has to wonder why Sango and Miroku even bothered to come along with Inuyasha, as their attacks eventually became utterly useless against Naraku and they were pointlessly risking their lives.
* [[BigCreepyCrawlies The Vajra]] in ''Anime/MacrossFrontier'', in episode 17, survive a direct hit from a ''nuclear weapon'' because it had been used against them a few episodes earlier.
** And yet Mecha sized K-bars Knives which have been used the entire series still work just fine on them... That said this isn't as insane as it sounds nor is the feat nearly as impressive as it sounds if one considers the actual physics involved. [[http://www.projectrho.com/rocket/rocket3x.html#nuke Read this and be enlightened]]. Executive Summary: Nukes aren't nearly as lethal in space and the range at which they'll do noticeable damage to anything even vaguely armored is surprisingly short. Nor were the hits in question really direct at least on those we see survive (and going by the stock footage used for the blast not all of them did...) as the missiles looked to be fired more for proximity detonation in the enemy formation then direct impacts.
*** Said range actually measures in tens or hundreds of kilometers even for the basic nukes (an elbow-pushing distance even at LEO), and reaction weaponry in Macross is, in fact, antimatter, that has much greater range. All this doesn't make much sense, but then, do the space battles as they are shown there really [[RuleOfCool have any sense whatsoever]]?
*** No it doesn't range is related to yield as both are just radiation bursts. Actually anti-matter will waste allot of energy if used as a proximity weapon as many byproducts quickly degrade to non-lethal particles within a very short distance. It makes no difference though as footage for the later attacks shows that even after they adapted the weapons were still vaporizing them if they were reasonably close to the blast. That's not what I call immunity.
*** Back on the knife thing, don't forget that the knives are supported by the Valkyrie's point barrier system, which basically lets it cut through armor like butter. It's basically a [[TabletopGame/{{Warhammer 40000}} Power Knife]].
* Byakuran in ''Manga/KatekyoHitmanReborn'' used this to an extend. He just didn't wait until someone used a certain tactic against him, he simply communicated with himself in alternate dimensions and linked their minds together to make himself crazy prepared for anything.
* Nurarihyon from ''Manga/{{Gantz}}'' had this as his power. In addition to adapting to become immune to attacks, he could also beat fighters at their own game by BiggerStick adaptation. [[spoiler:It turns out that he can't adapt to attacks that he can't see coming. The Gantz combatants snipe him to death.]]
* [[spoiler:Aizen]] from ''Manga/{{Bleach}}'' became something like this. Every time he became injured or close to death, the Hogyoku gave him a new form to counter it. At least until[[spoiler: [[HoistByHisOwnPetard the Hogyoku got sick of it and withdrew its support]].]]
* In ''Anime/ElHazardTheMagnificentWorld'', Ifurita seems to become immune anytime she's hit with a magic attack. And then she uses it on you...
* Gourmet Hunters in ''Manga/{{Toriko}}'' have this due to being infused with Gourmet Cells as well as their personal abilities. Most of them have AcquiredPoisonImmunity due to this.
* Kira Yamato with his [[spoiler: Ultimate Coordinator]] abilities in GundamSeed. With his increased thought process speed and reflexes, he could reprogram his Gundam's Operation Systems to optimal efficiency matching his environment and situation, in mid-battle.
* The character Fraulein Kreutune from ''LightNovel/ACertainMagicalIndex'' has a brain that rapidly absorbs information from her surrounding environment, then her body slowly evolves.
[[/folder]]

[[folder:Card Games]]
* In the ''TabletopGame/MagicTheGathering'' universe, the Slivers' more prominent traits were their fast evolution rate, adapting to overcome anything thrown at them. However, what made them so dangerous (both in the story and in game) was their species trait of ''sharing'' their adaptations with all other slivers in proximity.
** However, in-game, the slivers' abilities were conferred onto Slivers ''on all sides'', so a Sliver MirrorMatch could turn out deadly. Not to mention that there are some slivers with negative effects thrown in just to counter all-Sliver decks.
[[/folder]]

[[folder:Comic Book]]
* Doomsday and (in {{the Silver Age|OfComicBooks}}) the Calculator and the Shaggy Man from Franchise/TheDCU.
* Lots of anti-super robots in the Franchise/MarvelUniverse: later models of the mutant-hunting Sentinels (especially in the BadFuture of ''Comicbook/DaysOfFuturePast'', the Fury (from CaptainBritain's adventures), and the Shiva series.
* The [[MeaningfulName appropriately-named]] Darwin of the Comicbook/{{X-Men}} has this as his mutant power -- he will immediately mutate whatever he needs to survive. Immerse him in water and he'll grow gills, burn him and he becomes fireproof, poison him and his body chemistry shifts to neutralize it, etc. It's really too bad that it only happens as an unconscious survival mechanism; with control over that power he'd be damn near omnipotent. It should be noted that his powers don't always give him the ability needed to ''win'' a fight, only to survive. When faced with the Hulk, he gained the ability to [[ScrewThisImOuttaHere teleport to the next state]].
* Random, another Marvel mutant, whose other power was [[ArmCannon turning his hands into guns]].
* There was a robot called appropriately the Super Adaptoid that did this. In one comic, it was defeated by [[ComicBook/FantasticFour Ben Grimm]] who was his normal human self at the time, but wearing a [[PoweredArmor suit]] that still gave him SuperStrength. Ben Grimm tricked the Adaptoid into copying his normal human self, then used the suit's power to punch the Adaptoid out in one blow.
** An early X-Men comic during the Mimic's brief tenure as a hero pitted him against the Super Adaptoid, that had already perfected the abilities of the Avengers. After beating everyone else, including Professor Xavier, the Adaptoid fought the Mimic to a standstill until the Mimic threw the match and psychically convinced the Super Adaptoid to copy his powers. The Mimic's own power was to copy other people's powers, just like the Super-Adaptoid. The attempt to copy that power exceeded the Super-Adaptoid's capacity to duplicate. The feedback also temporarily shut down the Mimic's powers.
* Apocalypse caused battles for evolutionary purposes. When the X-Men beat his men, he thanked them for weeding out the weak.
* SelfDemonstrating/{{Lobo}} has this, as a side-effect of his HealingFactor. As with most of his powers, how effective or what it works ''on'' varies wildly between stories and writers. One notable problem arose when a magic spell de-aged him, and also resulted in him become immune to that kind of magic. Unfortunately, the traditional ''cure'' for his condition was from the same type of magic... And Marvel's even-further-over-the-top Lobo parody [[http://www.marvunapp.com/Appendix2/lunatikmerc.htm Lunatik]] has been adapting for six hundred million years, having started as a microbe and eventually eating all life on his homeworld.
* The UltimateMarvel version of Comicbook/IncredibleHulk has this to a degree-- he has adapted to environments as extreme as the (simulated) surface of [[DeathWorld Venus]]. This is also the reason why his condition can't be cured -- his body adapts to whatever agent is used to prevent the change. Mainstream Hulk has this too, but to a lesser degree and with less consistency since it's one of his lesser known/used/liked powers. He's been shown adapting the ability to breath under water and survive the vacuum of space for extended periods.
* Another X-Men mutant, Lifeguard, gets whatever power is needed to save ''someone else''.
* Marvel's alien Kree were stuck in an evolutionary dead end, unable to adapt or mutate; so after trying a number of less-than-ideal solutions ([[NoBiochemicalBarriers breeding hybrids with other species]] led to [[AllOfTheOtherReindeer social stratification and prejudice]], setting off a mutagenic bomb led to-- well, a huge frikkin' ''bomb'' that killed half their population and left most of the rest sick and dying) they eventually turned themselves into the Ruul, who can self-adapt to any condition. Later writers seem to have undone most of this for no apparent reason.
* One of Comicbook/SpiderWoman Jessica Drew's original powers was that she became immune to any poison after being affected by it once.
* Comicbook/{{Legion of Super-Heroes}} member [[spoiler:and eventual traitor]] Nemesis Kid had the power to gain whatever abilities were needed to defeat any single opponent. [[spoiler:This backfired when he faced Projectra, after murdering her husband Karate Kid. His powers gave him the ability to see through her illusions, but when he tried to gloat over her helplessness, she [[Awesome/{{LegionOfSuper-Heroes}} snapped his neck with her bare hands]].]]
* Whenever DC's ResurrectionMan is killed by something, he is reborn immune to the way he died. In fact, when he was killed by extreme pain, [[GenderBender he came back as a woman]], because women are [[ScienceMarchesOn supposedly]] more resistant to pain.
[[/folder]]

[[folder:Fan Fic]]
* [[FanFic/HereBeDragons Here Be Dragons]] Taylor's power starts out as a minor version of this, logical, due to possessing [[spoiler: Lung's transformative powers]]. Later, [[spoiler: Contessa]] forces a second trigger event, giving her a far more potent version of this ability.
* Freddie gets this power in ''[[http://www.fanfiction.net/s/8532906/1/iFightCrimeWithVictorious iFight Crime With Victorious]]''. Useful, considering his number 1 aggressor aka Sam Puckett now has superhuman strength to torture him with.
* Taken to its logical extreme and closing off all loopholes along the way: The ''Manga/RanmaOneHalf '' fanfic ''[[http://www.talesfromthevault.com/relentless/ Relentless]]'', where the [[EldritchAbomination Reikoku]] has this ability. It's an unusual take as in the story, the Reikoku adapts to the characters' [[SupernaturalMartialArts techniques]]
[[/folder]]

[[folder:Films -- Animated]]
* Syndrome's robot in ''WesternAnimation/TheIncredibles'' was rebuilt between beatings. Hero A would do X to it and destroy it. Mark II is built without a weakness to X and beats Hero A. Hero B does Y to it and destroy it. Mark III is built without a weakness to Y, and so on. There is an EasterEgg on the DVD that shows all the different versions and who destroyed them. There's also a scene in the movie where Mr. Incredible finds the computer showing which versions killed what heroes. It was also able learn to avoid tricks that worked against it before, but that really only made it as smart as the people it fought.
[[/folder]]

[[folder:Films -- Live-Action]]
* The Xenomorphs from ''Franchise/{{Alien}}'', as they have the ability to breed with any organism and take [[LEGOGenetics genetic material]] from them, thus adapting to whatever environment the organism in question comes from.
* The enemy in the 2001 film ''Film/{{Evolution}}'' and its AnimatedAdaptation, ''WesternAnimation/{{Alienators|EvolutionContinues}}''.
* ''Film/XMenFirstClass'' portrays Darwin's abilities in full. Ironically, [[spoiler: he also succumbs to BlackDudeDiesFirst.]]
[[/folder]]

[[folder:Literature]]
* In ''Literature/MySistersKeeper'', this reason is used to explain why none of the treatments for Kate's leukemia work more than once.
* In the ''Literature/SwordOfTruth'' series, [[spoiler:the beast from the underworld]] is said to adapt to prevent one strategy from working on it more than once. Ironically this works to its detriment--while a given strategy only works once, as a creature of chaos its methods and weaknesses are totally ''random''. On at least one occasion, it had the heroes entirely dead to rights, but for the fact [[DeusExMachina its current form dissolved in water, discovered just as it starts to rain]].
* In the novel ''Literature/{{Meg}}'', blinding the giant shark made it deadlier, as its other senses compensated for its blindness and now it could hunt during the day.
* In ''Literature/LastAndFirstMen'', the Martians do this while fighting the Second Men. [[SciFiWritersHaveNoSenseOfScale Over the course of several thousand years, naturally]].
** The shorter timescale is partly down to the Martians' very unusual biology and partly due to the fact that [[ScienceMarchesOn genetics was very poorly understood when the novel was written.]] The structure of DNA wouldn't be identified for another quarter century, for example.
* In Creator/GregEgan's ''Teranesia'', an evolving organism is apparently able to anticipate future challenges and develop appropriately.
* In Stephen King's ''Literature/TheStand'', what made the superflu different from the normal flu (and much deadlier) is its ability to change to fight the antibodies the human organism generates to fight the virus, until your defenses can't stand anymore.
* This trope is played for tragedy and to kill all remaining hope in the sci-fi novella ''With Folded Hands...''. A man creates a perfect race of robots to cater to humanity and stop them from killing each other after his home planet was wiped out by civil war. It works too well and the robots begin stripping humanity of its freedom, planet by planet. A man uses rhodomagnetics, the force discovered by the creator and what allows the robots their highly advanced functions, to slip under their radar and attempts to assassinate the creator for dooming mankind. He's stopped, and the creator [[MyGodWhatHaveIDone only then realizes what the robots are doing]]. He jumps from colony to colony, staying ahead of his creation while attempting to create a weapon that will destroy his lifeless homeworld, where the central network is located. He finishes and fires the weapon, only for it to fail. Robots arrive at his residence and inform him that after the assassin, they engineered a way to detect and neutralize rhodomagnetics applied against them, effectively shielding the planet from the weapon. [[DownerEnding This dashes mankind's only hope to free itself from the robots.]]
* The Vord in ''Literature/CodexAlera'' definitely qualify. When we first run into them, they're a bunch of creepy spiders who spin wax instead of webs. Then there are big warrior beetles, and little spiders that can [[PuppeteerParasite take over your brain,]]. And that was back before they got scary. They could quickly create entire new species and [[ExplosiveBreeder generate massive numbers]] of them. They see human knights in armor? Suddenly there are heavily armored humanoids with swords to fight them. Make a wall of shields? Now there are enormous mantises with [[SinisterScythe sickle-arms]] that can reach over the shields and disembowel you. Oh, you can fly with magic? How about warriors with [[WingedHumanoid dragonfly wings]]. Team up with huge wolf-men? That's okay, we've got a [[LightningBruiser vord]] for that too. Build a massive wall just to keep us out? How about a Vord the size of a ''[[AttackOfThe50FootWhatever Gothic cathedral]]'' smashing into your wall! Wow, good thing you have that amazing magic that we can't quite seem to get hold of... [[OhCrap oh]]. [[AwesomenessByAnalysis Nevermind]].
** And to make matters worse, they're [[AbsoluteXenophobe obsessively xenophobic]], want to TakeOverTheWorld, aren't fussed about whether they do it by [[AssimilationPlot assimilating us]], [[KillEmAll slaughtering us]], or [[IAmAHumanitarian sticking us in wax to digest to death]], and are [[HiveMind controlled]] by a Queen who's the [[UncannyValley stuff of]] nightmares [[PsychopathicManChild all by]] [[AGodAmI herself.]]
* The Inhibitors in Creator/AlastairReynolds' RevelationSpace Verse have this ability, there's some interesting character speculation about whether they are really adapting or whether they're downloading countermeasures from an extant database whenever they encounter a new weapon
* The sword of Gryffindor in ''Literature/HarryPotter'' can't be destroyed; it simply takes in the power of whatever it encounters. For example, when in ''The Chamber of Secrets'' [[spoiler:Harry uses it to kill the basilisk, it becomes imbued with basilisk venom]].
* The Vlagh and its creatures in Creator/DavidEddings' Dreamers. They adapted to every trick the protagonists use in the previous battles... only to have them devise more. They also forage the battlefield for dropped weapons. Eventually they evolved to the point they had [[spoiler:eight arms on some of the creatures... each carrying four bows]]. This caused the protagonists some anxiety. [[spoiler: [[TooDumbToLive At least until they saw the creatures using the bows...as maces.]]]]
[[/folder]]

[[folder:Live-Action TV]]
* The Borg from ''Series/StarTrekTheNextGeneration'' are explicitly described as being able to adapt to anything used against them, so most weapons will only work two or three times before they're useless.
** [[RockBeatsLaser Melee attacks have a better chance of succeeding.]] Not always, as one unfortunate RedShirt tried to [[PistolWhip rifle butt]] a drone and got trounced, and Data rampaging in Engineering got him thrown behind a forcefield.
** Also note that in ''Elite Force'', Seven came up with the [=IMod=] (Infinity Modulation Weapon), a weapon with infinite, random energy signatures that change after every shot to take out the Borg.
*** The [=IMod=] only works because it unleashes devastating energy in a single burst (at least against the Borg), and also automatically changes energy signatures. Normal phasers and phase rifles can do the same thing as the [=IMod=], but must be manually changed to new frequencies, and are limited in power. Human (and alien) imagination being what it is, it's not possible to keep coming up with random frequencies.
**** Except maybe by randomly punching keys.
*** In the first mission of the sequel (taking place in parallel with the GrandFinale of ''StarTrekVoyager''), the Borg aboard the sphere come up with a counter to the I-MOD by generating an interference field that disables the weapon, forcing you to rely on other weapons and use them sparingly.
* The Cybermen of ''Series/DoctorWho'' have always had traits of TheAssimilator, but this aspect gets focused on in the incarnation introduced in "Nightmare in Silver". Sometimes you'll take a few of them down before they adapt - others, it won't cost them a single unit.
* An episode of ''Series/TheOuterLimits'' (the 90s series) had a man infested with {{Nanomachines}} programmed to heal and protect his body, which they did [[LiteralGenie mindlessly and efficiently]]-- he nearly drowns and grows gills, he gets beaten up and grows extra layers of bone, and his skin develops poison glands like a jellyfish, so ''no one can touch him''...
** They also, for some reason, decide that having a limited field of view is a flaw, so they grow an extra pair of eyes on the back of his head.
* ''Series/{{Smallville}}'''s version of Doomsday, like his comic counterpart, has this ability; as his "mother" Faora put it, "What kills you makes you stronger".
* The Replicators from ''Series/StargateSG1'' have essentially the same adaptability level as the Borg from ''Franchise/StarTrek''; they, too, cannot seem to adapt to [[KineticWeaponsAreJustBetter being shot with a machine gun]], until Season 5...Viva La Evolution!
** Ditto for their cousins the Asurans in ''Series/StargateAtlantis'', although they are already in humanoid form when they encounter the Atlantis team.
* ''Series/MightyMorphinPowerRangers''
** The War Zord Cyclopsis acted like this after it was rebuilt by Lokar. In a bit of a subversion, that "evolution" disappeared after the Rangers retreated and when they came back to fight, they knew how to overcome it (rapidly switching tactics). "Overload! Overload! Too many changes!"
** Hatchasarus was repeatedly destroyed and would reassemble with more bling (though not necessarily directly related to what had killed him before.) He can't be taken down for good until Cardiatron (the giant, floating ''heart'' that is its central computer) is destroyed.
[[/folder]]

[[folder: MultipleMedia]]
* Reidak from the ''Franchise/{{Bionicle}}'' series.
[[/folder]]

[[folder:Radio]]
* Parodied by the Haggunenons in ''Radio/TheHitchhikersGuideToTheGalaxy'', who would shapeshift into seemingly random "adaptations" because they have "the most impatient chromosomes in the Galaxy".
[[/folder]]

[[folder:Tabletop Games]]
* The epic level [[TabletopGame/DungeonsAndDragons D&D]] monster, the Infernal, has this as a specific power, only able to be affected by a spell once from the same spellcaster.
** At lower level there is the skindancer, which has pretty good resistance to the last weapon type that struck it, and the last magical energy type that affected it.
** In the red box edition, the master's level book described the Adapters, who develop a temporary immunity when struck by an elemental attack.
** In 4th edition, all demon type enemies gain the ability to immediately become resistant to any elemental energy type attack (acid, cold, fire, lightning, thunder) after you hit them with it once. So something that doesn't put them down on the first hit will be much weaker against them the second time.
* ''TabletopGame/{{Warhammer 40000}}'' has the Tyranids:
-->"We fought them the first day, and our guns tore through them with ease. We fought them the second day and saw our missiles bounce of a thickened skin they seemed now to bear, so we turned our lances on them. We fought them the third day, and no cursed thing worked!"
** Even worse: Not just one of them, but at least ''that entire fleet'' you are fighting can get that characteristic.
** The Tau were able to exploit this: by getting their Kroot allies to take on Tyranids in forests, particularly agile but also rather fragile Gaunts were produced that had adapted extremely well to fighting arboreal warriors...then they drew the 'Nids out of the forests and opened up with their usual array of {{BFG}}s.
* ''Mechanon'' is a standard recurring (and overarching) BigBad from ''TabletopGame/{{Champions}}''. Each time he is defeated (even if destroyed, he's rebuilt), he returns immune to the last attack that killed him, and often with weapons to which his prior nemesis is particularly vulnerable. If fought long enough, he truly becomes unbeatable.
* Unsurprisingly, ''TabletopGame/MutantsAndMasterminds'' features a power or two for this. "Adaptation" works like it says. Then there's "Nemesis"- every round you pick one person to be your nemesis, and you get X points worth of powers suited to fighting them (X being based on your power rank). The catch is that while you are free to suggest things, the GM has final say on what you get, and can distribute things however he likes (he could give you one strong useful power, 2 medium-strength, fairly useful powers, 10 weak powers of varying helpfulness...)
* In ''TabletopGame/{{Exalted}}'', one Charm the Lunar have allows them to render themselves immune to the first weapon classification to hit them in a scene. This is somewhat mechanically awkward because weapons aren't classified in a way that makes this make sense as it's written[[note]]according to some readings, a punch could render you immune to all bludgeoning weapons, or to all martial arts weapons, or to all non-artifact martial arts weapons and so on[[/note]], but it's the thought that counts.
[[/folder]]

[[folder: Video Games]]
* ''VideoGame/ResidentEvil6'' introduces a new species of [=B.O.W=] called the J'avo that can do this, with about a dozen different mutations that can occur depending on if you've been targeting their arm, legs, torso or head. Plus, multiple mutations can occur on the same J'avo, so you can give them two different arm mutations, a head mutation, a torso mutation, and legs mutation. Plus, there's a rare chance of them cocooning themselves to undergo a "Complete Mutation", emerging as a coherent but much tougher variant of [=B.O.W=], with several different outcomes, ranging from the armor-plated LightningBruiser Napad to the dart-throwing, {{wall crawl}}ing Strelat.
* Pringer X, the ultimate bonus boss in the remake of ''VideoGame/{{Disgaea 2|Cursed Memories}}'' and ''VideoGame/{{Disgaea 4| A Promise Unforgotten}}'' possesses an ability that makes it completely immune to whatever special attack it was hit by for the rest of the battle. Made more complicated by the fact that when you fight more then one of them at the same time later on, all of them become immune to the attack.
* Cubia from the first four ''[[Franchise/DotHack .hack//]]'' [=PS2=] games.
* Most [=RPGs=] have at least one boss that adapts to the elements you attack them with, resulting in a literal ElementalRockPaperScissors as you try to switch the elements of your attacks to be the opposite of your last one or whatever it has shifted to. Can be frustrating if you misstep, because the wrong element will usually fully heal the boss.
** The Tetramorph in ''VideoGame/FinalFantasyX''.
** At least one monster in every other ''Franchise/FinalFantasy'' game as well.
** Most ''Franchise/FinalFantasy'' bosses are actually a variant: they're weak against one specific element and absorb all others, but can randomly change the element they're weak against. This is usually called "Wall Change" or "Element Change" or something similar.
** ''VideoGame/BreathOfFireIII'' has a lot of these as well.
** Magus in ''VideoGame/ChronoTrigger''; the Golem boss not only defends against the attack type used on it, but begins attacking using that type.
*** It's possible to use Golem's copy attack against it: by getting the right equipment and using the right attacks, it's very easy to force Golem to use attacks that are very inefficient against you. In a NewGamePlus, it's stupidly easy to force Golem to use attacks that ''heal'' you.
* ''Franchise/{{Pokemon}}'' has two: the Porygon series and Kecleon.
*** More specifically, Porygon2's Conversion2 move and Kecleon's Color Change ability. Conversion2 is rather more limited, since the nature of Pokémon's ElementalRockPaperScissors means that the type it changes to is randomly chosen from the types that resist the last attack. Color Change is a more typical example.
*** Ironically, since Ghost and Dragon-types are weak against themselves, using such a move on Kecleon actually makes it weaker to these attacks then it was before (It starts off respectively immune and neutral to them). Oops.
*** Variations of the glitch [[TheMissingno MissingNo.]] had no [[ElementalRockPaperScissors type]] themselves, and therefore took the type of the last Pokemon loaded.
*** There's also an ability called Adaptability, but it only powers up move of the same type (more than usual).
*** The ability Download boosts the attack stat of the Pokemon based on which of the defense stats of the opponents is lower.
** This is, in fact, what the AI will do to you in the Battle Tower, Battle Frontier, Battle Subway, Battle Maison, and so forth: If it observes that you are having problems dealing with a certain Pokémon or Pokémon type, it will assign upcoming trainers more of those Pokémon. The AI will also examine the Pokémon you bring along and attempt to find Pokémon that can most effectively deal with all of the ones you bring along.
* The fallen Levant's (OneWingedAngel?) monster form in ''Jade Cocoon 2'': he occasionally gains immunity to the element of the side of the [=BeastAmulet=] that's been used to attack him. When this happens, he summons a pair of lesser Divine Beasts of the same element he just immunized himself against and they prevent you from attacking him by becoming the only available targets. Attacks with any other element will damage him as normal, [[ElementalRockPaperScissors and attacks of the opposite element are particularly effective]], but a few turns after the lesser Beasts have both been killed, the cycle repeats. So the fight continues until you've defeated him.
* ''VideoGame/WarningForever'' has this as its main mechanic: a time attack boss rush where the boss repeatedly comes back stronger in a way that seeks to counter how the player destroyed it in the last round. For example, if it was defeated by having its rear armor destroyed, its next form will have more armor on its rear. It also changes which weapons it adds depending on how effective they were (e.g. if it killed the player using lasers frequently in one round, expect it to have a lot more lasers in the next round).
* Warlock Nether Protection and Death Knight Acclimation talents in ''VideoGame/WorldOfWarcraft'' work somewhat like this. They have a chance to reduce the damage taken from the school of the last spell that hit you.
** There's also some creatures, notably certain types of Voidwalkers, with an ability like this. Hit them long enough with one spell school and they not only gain an immunity for that type of damage, but can now use an [=AoE=] spell of that type.
* Arcueid from ''VisualNovel/{{Tsukihime}}'' claims such an ability. She was immune to conventional weapons to begin with, and gained immunities to conceptual weapons as they were used to fight her. When Shiki killed her, she was sure he used some obscure far eastern conceptual weapon. In a slight subversion, she can't become immune to that particular ability, either.
** The manga adaptation gives the same ability to Roa, a vampire (accidentally) created by Arcueid. He demonstrates it in his battle against Ciel - by the end of the fight, her signature Black Key swords have become so ineffective that being impaled by several dozen at once barely phases him.
* In the ''VideoGame/NexusWar'' spinoff ''Worlds In Global Battle Locked'', Nexus Champions can do this with their aptly named Tattoo of Adaptation, something they didn't have in the original.
* In ''Videogame/{{Nethack}}'', you. If you manage to kill a red dragon, eat his corpse, and you're immune to fire. The next red dragon's fire breath might damage your equipment, but will not do much damage to you. Same goes for several immunities.
* This is pretty much the point of the Zerg in ''Franchise/StarCraft''. Notably, their upgrade building is called the "Evolution Chamber," in which the Overmind pits hundreds of zerg warriors against each other and only keeps the strong, and is also the fluff explanation for the origin of Banelings.
** In the campaign of ''VideoGame/StarcraftIIHeartOfTheSwarm'' approximately half the evolution missions involve zerg exposed to various environmental hazards (acid pools, lava, [[NuclearNasty experimental nukes]]...) in order to grant them new abilities. In the other half the zerg absorb DNA from creatures they [[CannibalismSuperpower consume]].
* Berserker from ''VisualNovel/FateStayNight'', Unless you are TheHero (or his FutureBadass) or [[Literature/TheEpicOfGilgamesh King Of Heroes]], you will probably fail to kill him.
* In ''Videogame/{{Spore}}'' you edit your creature throughout the cell and creature stages to give them the highest chance of survival.
* Story-wise, there is a promotional ITEM for ''VideoGame/DragonAgeII'' that does this; The Belt of Hindsight. The trailer for this belt says that it analyzes the deaths of its wearers, and develops magic defenses to slightly protect future wearers against what it was unable to block before. Current resistances when obtained by Hawke include Fire, Poison, Stabs, and Witches. Don't ask, just read the obituary on the leather, magically scrawled in lyrium ink.
* Mockingbird's power in ''VideoGame/MarvelAvengersAlliance'' is to [[TacticalRockPaperScissors switch to the opposing class]] of any classed character that attacks her.
* This trope is the true source of VideoGame/MegaManX's "Limitless Potential"; he was revolutionary in robotics as he had the ability to learn and grow in strength when [[VideoGame/MegaManClassic previous robots]] had their minds and power levels pre-determined by their creators. [[BigBad Sigma]] takes interest in his potential, and decides to instigate a reploid revolution in order to [[EvilutionaryBiologist evolve reploids to their fullest potential]].
* Jr. Troopa in ''VideoGame/PaperMario'' is a minor version. He starts off pretty incompetent. As the game goes on, however, he will acquire new powers to counter abilities Mario uses against him, combining them together late into the game. That being said, he remains rather incompetent throughout the whole game, as while he can adapt to limit Mario's ability to fight him, Mario keeps gaining ''more'' techniques that render him a joke again.
* In ''Enemy Infestation'', the entire gameplay is based on the fact that the aliens mutate so fast that every mission, the effects of the weapons ([[RockBeatsLaser except for two]]) on them are completely unpredictable. Last mission, they dropped from a raygun shot. This mission, the raygun causes the aliens to split in two or grow, while what kills them is pointing a remote at them and clicking. Next mission, the remote does nothing and they need to knocked out by a bug spray... well, you get the idea.
[[/folder]]

[[folder:Web Comics]]
* Oberon from the Webcomic ''Killroy and Tina'' would always come back with the properties of whatever "killed" him. The only way to permanently kill him is to throw him into a black hole (so he comes back as nothing). Unfortunately, he [[OhCrap falls into a star instead]]. Just think, if the series hadn't been [[OrphanedSeries cruelly abandoned]], something ''might'' have come of it.
** There are the ArcWords "illumination goes boom".
* Aylee from ''Webcomic/SluggyFreelance'' (although her adaptations may involve spending months in a cocoon).
[[/folder]]

[[folder:Web Original]]
* [[http://scp-wiki.wikidot.com/scp-682 SCP-682]] of the ''Wiki/SCPFoundation'' is a reptilian [[HealingFactor regenerating]] OmnicidalManiac who also possesses this power. They try to shoot out it's eyes, it grows several new sets covered in armor plating. They try to poison it, it starts spraying out jets of high-pressure blood to get the poison out. Thankfully, the adaptations wear off after a short while.
** This is the main reason they refuse to use [[NukeEm nuclear weapons]] on it: if it survives, it'll be immune to pretty much ''anything.''
** 682 actually makes an interesting addition to this trope: often when it adapts to whatever is used against it, it is then able to use the adaptation as a weapon. They refuse to use a portable black hole against it for fear of how it might be able to retaliate if it survived.
** It's more than just survival, too, as evidenced by their attempts to make 682 [[ItMakesSenseInContext believe that he's a toaster]]. They didn't count on him consuming all the bread offered and [[FunnyMoments proceeding to projectile-vomit it out, toasted to perfection]].
** The Foundation once tried to kill it by using an [=SCP=] with the [[RealityWarper power to change the universal constants of physics]]. 682 not only adapted to survive as it always does, it found the experience ''fun''.
* In the GlobalGuardiansPBEMUniverse, Mexican superhero Evolucion, is a FlyingBrick with "reactive evolution" powers. He gains those defensive and sensory powers he needs depending on the situation he finds himself in (he gains night vision in darkness, he grows gills if he's underwater, fireproof skin if he's in a fire, and so on).
** The {{Super Robot|Genre}} Omega, from the same setting, is programmed to redesign himself after ever defeat so he cannot be defeated by the same method twice.
* In ''Literature/{{Worm}}'', Crawler of the Slaughterhouse Nine combines this with a massive HealingFactor, one which lets him fully regenerate within seconds of being harmed. He deliberately throws himself into harm's way in order to become stronger. At one point, he's exposed to a nanothorn attack that takes most of his body apart on a molecular scale...which causes the destroyed portion of his body to grow back with ''biological nanomachines that can disintegrate anything he touches.'' [[spoiler:The heroes only manage to kill him by carpet bombing the area he's in with [[TheSparkOfGenius super]][[MadBomber -villain]] [[HavingABlast made]] bombs]]
* Literature/Brennus has Desolation-In-Light and her sister Gloom Glimmer have the power to posses several superpowers appropriate to the situation.
[[/folder]]

[[folder:Western Animation]]
* The android Amazo in ''WesternAnimation/JusticeLeague''. [[AGodAmI Eventually gets so many powers he doesn't know what to do with them and decides to become a philosopher]]. Doomsday to a lesser extent as per his comic counterpart. Try to lobotomize him with heat vision? His skull thickens in time for the next fight.
* Shane "Goose" Gooseman from ''WesternAnimation/AdventuresOfTheGalaxyRangers'' had this power combined with his {{Shapeshifting}}, due to being a genetically engineered SuperSoldier with a [[UpgradeArtifact Series Five Implant]] that also acted as a RestrainingBolt if need be.
* In the 2007 ''Comicbook/DoctorStrange'' animated film, Strange has the innate ability to absorb and adapt a defense for any magic thrown at him. Thus he goes from on-the-skids Muggle to Sorcerer Supreme in the course of one film and a grand total of one BossBattle.
* In the third ''WesternAnimation/JimmyTimmyPowerHour'', the two create their own supervillain to fight, but accidentally gives him this power because of a typo.
[[/folder]]

[[folder:Real Life]]
* Your own immune system adapts to infections. A vaccine is a weakened sample of a virus, your immune system uses it to learn how to combat the non-weakened version. As a result, you are unlikely to get any particular virus more than once. Chicken pox is a classic example, and since it's much more dangerous to adults, it's recommended to expose kids to reduce the chance that they'll get it after they grow up.
** Inverted by the [[http://en.wikipedia.org/wiki/Original_antigenic_sin original antigenic sin]] where a prior mismatched infection makes the future related infection significantly worse.
* Other parts of our body respond to damage by rebuilding the affected tissues and structures with greater strength. Repeatedly damaged skin forms calluses. Exercise causes muscle damage and stress, so the muscles rebuild with greater strength. Damaged bone will rebuild itself with greater density.
** Some martial artists train themselves by striking at hard things. This will damage their bones, which rebuild. This leads to people who can smash bricks with their heads and have skeletons visibly different. Serious Muay Thai kickboxers kick trees.
*** Overdoing it tends to leave the practitioner with serious health problems later in life, as the body simply cannot cope with the stress. However, with no stress on bones and muscles at all (such as happens without gravity) leads to them turning brittle, weak and ultimately none serviceable. Like all things, best utilized in moderation.
* Any population of organisms evolve. The word "evolution" is older than the concept of biological evolution. This is slow, noticeable changes to the environment usually take several generations at least.
** Bacteria reproduce quickly, and evolve quickly as a result. Biologists study bacterial evolution in a lab because they don't have to wait too long for the results. Bacteria can also develop resistance to antibiotics quickly -- which is why doctors tell you to finish your entire antibiotics prescription instead of stopping when you feel better. If you finish it all, there's a good chance you've wiped all the bacteria out. If you don't finish the prescription, the bacteria remaining may have evolved a degree of resistance and the next course won't be as effective.
*** So when you're taking antibiotics, think of the bacteria as your typical shonen hero, and antibiotics as your signature move. Wipe them out before they can learn to counter your signature move.
**** More to the point, [[BondVillainStupidity don't stop to gloat when you've got them on the ropes]] -- just kill them.
** An inversion to that is single sex animals. While they gain several benefits over single sex organisms for a species, the main reason why they are so rare is because a dual gendered species can evolve much faster than a single gendered species.
[[/folder]]

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