History Main / IncreasinglyLethalEnemy

-->'''Mirage:''' [[TryNotToDie And don't die.]]
-->'''Mr. Incredible:''' Great. Thanks.

* A common problem in ''LightNovel/SoImASpiderSoWhat'', especially with boss monsters. Since continual exposure to threats allows you to unlock resistance skills, Kumoko has to kill her foes quickly before they grow immune to what she's using. Fortunately this goes both ways, as Kumoko also grows in power as she fights.

* ''WesternAnimation/TheIncredibles'': The Omnidroid is stated by Mirage to be an example of this trope:

** Annihilape has the move "Rage Fist" which builds in power whenever Annihilape takes damage. It starts innocently enough at base 50, but if Annihilape survives 6 hits (Difficult, but far from impossible with the right build) it will have a massive base 350 power, 100 points more than the next best score, ''''''EXPLOSION!'''''

* ''VideoGame/{{Elsword}}'': The BonusBoss Alterasia Type-H is infamous for this. He's surround by constantly spawning Alterasia Spores which periodically heal him. Failing to stay on top of them can cause him to be healed constantly.

* ''VideoGame/KingdomHeartsII'': Lexaeus' gimmick for his BonusBoss fight in the ''Final Mix'' version is that he has a power level that determines his damage output. He starts off doing so little damage that even if you're Level 1 he's completely non-threatening, but as the fight goes on he will occasionally power himself up and do more and more damage.

* The BonusBoss in ''VideoGame/LufiaIIRiseOfTheSinistrals'' is completely harmless for three turns, saying supportive things and even healing the party. On the fourth turn, he casts a spell that inescapably causes a TotalPartyKill, though thankfully it doesn't cause a game over, merely sends everyone back to the beginning of the 99-level BonusDungeon without their final reward.

* BonusBoss Lucifer in ''VideoGame/DevilSurvivor'' has to be defeated quickly once he goes into his second form, as he will periodically cast Megidoladyne, an [[InfinityPlusOneElement Almighty-elemental]] spell that targets everyone in all of your parties on the map and does 50% more damage with each successive casting, until it inflicts [[TotalPartyKill four-digit damage in a game where player-controlled characters can each only have up to 999 HP]].

* ''VideoGame/EtrianOdyssey IV'' introduced Rare Breeds, glowing variants of normal {{Mooks}} and [[BossInMookClothing F.O.E.s]] that get stronger the longer you leave them alive. They also give your party [[MetalSlime much more experience points than normal, provided they don't run away first]].

** In a different sort of [[VillainProtagonist enemy]], the Bio-Weapon plague will get increasingly deadly no matter what you do, and quickly becomes so quick at killing it can't infect fast enough and burns itself out. The key is to keep developing supression genes that will keep the lethality down for some time at least, until you've managed to infect enough people. And, if you infect everyone, you can just bring back ''all'' the lethality back [[OneHitKill and then some]] by unlocking the Annihilation Gene, which can and will kill the world in two weeks if everyone's caught the disease.

* The Nergigante of ''VideoGame/MonsterHunter'' is covered in spikes that regrow continually. It can shoot these spikes as well, and the bigger and harder they get, the more damage they deal to you. Beware when the spikes are completely black, ''especially'' once it does its [[ThatOneAttack infamous]] dive-bomb move. The Ruiner variant ditches this mechanic and instead has "ironspikes" that are impenetrable to all but the sharpest of weapons, but ''don't'' grow back once shattered.

* Letting an Engineer robot get set up in ''Team Fortress 2's'' Mann vs Machine mode means the robots get free teleports, cutting down the time you have to prepare for each spawned wave. Worse, they're invincible when spawned, so you could have two dozen Scout robots run in with a bomb in their midst and you might find yourself quickly overwhelmed.

* ''Junkworld'' has enemies called Abominations, mutated stags with moderately high HP and low attack which will attempt to mutate further after losing half their health. If they don't die before they finishes mutating, they turns into Abozombies, two-headed humanoid deer monstrosities that have ''far'' more health and attacking power.

* ''Junkworld'' has an enemy called the Abomination, a mutated stag with moderately high HP and low attack which will attempt to mutate further after losing half its health. If it doesn't die before it finishes mutating, it turns into a two-headed humanoid monstrosity that has far more health and attacking power.

* ''Junkworld'' has a mutated stag enemy called the Abomination, which will attempt to mutate after taking enough damage. If it doesn't die before this happens, it turns into a two-headed humanoid monstrosity that has far more health and attacking power.

* High-level paladins in ''VideoGame/WarcraftIII'' have a shield that makes them invulnerable and a mass resurrection ability. If not neutralized quickly, they spend the fight unable to take damage and bring back half a dozen dead units at full health.
** The Firelord's Incinerate ability deals ever-increasing damage with every attack.

* The FinalBoss of ''VideoGame/IttleDew'' has a phase where he summons [[DemonicSpider Petal Slugs]] over time. If left unchecked and this phase isn't defeated quickly, they can turn the boss arena into a BulletHell.

** The [[CanonImmigrant new canon version]] of Broly from ''Anime/DragonBallSuperBroly'' on the other hand, ''does'' have such an ability. When he's introduced, he's never been in a fight before. It's quickly revealed that when he fights he constantly grows stronger. And does it so quickly that he surpasses Super Saiyan Blue Goku and Vegeta as well as Golden Frieza, and it's speculated that he could even be a match for [[DestroyerDeity Beerus]]. This rapid increase in power means that Goku and Vegeta are forced to [[FusionDance become Super Saiyan Blue Gogeta]] to win.

* The Tonberry from the ''Franchise/FinalFantasy'' series will usually spend several turns approaching before using its signature "Everybody's Grudge" or "Karma" attack, which deals damage for [[WhatMeasureIsAMook every enemy defeated so far]] to one target. This attack can be OneHitKill for characters that have been murdering tons of enemies up to the point they can encounter Tonberries, which usually near the end of the game.

** Trials tend to have what are referred to as either "Soft Enrages" or "Hard Enrages". Soft enrages involve a damage dealing mechanic or otherwise becoming harder and harder to deal with as the battle drags on until it's impossible for the party to health through and continue, while a hard enrage is more simply defined: If the battle passes a certain timer, the boss wipes the party with an arena wise attack to prevent sub-optimal gameplay from succeeding at chipping away at a boss's health to victory

* Used for story purposes in ''Videogame/NierAutomata'' when you first fight Adam. He starts off as a barely functional, stumbling boss. But as the battle drags on, he analyzes what 2B and 9S do in order to gain more skill, which in the game looks like he's leveling up.

* The co-op bosses in ''VideoGame/OneHundredPercentOrangeJuice'' use a random card every turn to make things harder for the players, and as the match progresses these cards will gradually be swapped out for stronger ones. Each boss also has their own method of becoming more dangerous over time, such as Star Devourer dealing more damage to players in battle as she [[BanditMook steals more stars]] or Big the Johnathan covering the board in damage panels with his dive bomb attack.

* The loads of Master Ninja and Mechanists in ''VideoGame.FireEmblemFates'' Conquest Chapter 25 on Lunatic. Although Lunatic is the resident HarderThanHard mode, this level takes the cake. All the Master Ninja and Mechanists with debuffing shurikens will now get Inevitable End, which lets their ''debuffs stack'', giving your best units stats equivalent of a level 1 Mook. Have fun forcing your way across two hallways filled with these to kill two Master Ninja minibosses who get Avoid from their GeoEffects or else [[WeCannotGoOnWithoutYou Corrin]] will get slaughtered by the ludicrously overpowered DuelBoss on turn 20.

** All of the Extreme/Savage difficulty and some endgame normal mode Primals and Raids have an "Enrage" mechanic where if you take too long, the boss will simply OneHitKill the party, usually with an arena-wide AOE they've done before.