History ThatOneBoss / FirstPersonShooter

** The Headless Horseless Horsemann, the very first in a line of bosses, has an axe strike that is pretty much always a OneHitKill. There are only two things that can survive it: Dead Ringer Spies or a Wrangler-shielded level 3 sentry, and he'll attack again right after that. He can also scare you, slowing those affected and preventing them from attacking or jumping. And this is all accompanied by the fact that once he kills somebody, a random person is marked as his target. They can only transfer the mark by hitting somebody with their melee weapon. If they're slow, they're pretty much screwed. Also, he randomly appears out of the control point currently open. Imagine breaking through the defenses with barely any time left, miraculously holding off the enemies... and then have this guy rise out of the control point, completely throwing off any and all concentration. If you want a special item, you have to deal a hit with a melee weapon ''during his death animation''.

* In ''VideoGame/{{killer7}}'', there are two bosses that are much harder than the other bosses at least on the first attempt.

** The last two minibosses (though the first can arguably be considered a normal boss due to a regular boss not being present in its level) are worth noting. The Timer Smile forces you to hit certain parts on its body before it reaches you, which is easy... unless you didn't save a very easy to hit target, like the one on its head, for last, as once there's only one left, it TurnsRed and runs extremely quickly. Then, the Galactic Tomahawk Smile fires an unrelenting barrage of missiles that start becoming more and more frequent as it loses health and, once one hits, they all start coming and you have to start mashing the pause button to quickly heal.

'''NOTE:''' FinalBoss and WakeUpCallBoss cannot be ThatOneBoss without being overly hard by ''their'' standards. Please do not add them as examples. BonusBoss is completely banned. They are supposed to be overpowered and have no real standards.

* [[BigBad Maledict]] in ''VideoGame/Doom3: Resurrection of Evil''. You start the battle by landing on a flowing platform in the bottomless space of Hell. You have [[ArtifactOfDoom the Artifact]] but it's only in limited use. Maledict demands you to hand it over, but the marine simply points the gun at it. The battle start with Maledict randomly throwing fires and summoning the local cannon fodders at you, which you just simply kill and then use the Artifact to slow time and just fire whatever kind of guns right at Maledict's slow-flying ass. After a while, Maledict decides that he's gonna stop bull-shitting around and then just throws ''meteors'' at you, and all you can do is to avoid them and try not to fall over the platform, as well shoot the beast up. And you can't get any health packs during the battle.
* Cthon in ''VideoGame/{{Quake}}'' is a normally invincible PuzzleBoss that is defeated by three switches, when all previous enemies had been killed by brute force. You must run across narrow catwalks over lava to reach these switches, and Cthon tosses instant-kill lava balls at you that on higher difficulties are fired at where Cthon thinks you will be when they hit, and Cthon's guesses are uncannily accurate.
* In ''VideoGame/PerfectDarkZero'', Killian's personnel transport is an example of a first boss being the hardest boss, especially so on Perfect Agent and Dark Agent difficulties. Almost constant rain of machine gun fire, missiles that can damage you even when under cover, and [[TurnsRed when you've damaged him enough]], [[WeaponizedExhaust he starts burning you with his engine flames]].
* ''Franchise/{{Halo}}'':
** In ''VideoGame/{{Halo 2}}'', the Heretic Leader, particularly on the HarderThanHard Legendary difficulty. Equipped with a jetpack, near-instant-death dual Plasma Rifles, and multiple [[DoppelgangerAttack holographic doppelgangers]], all of which have jetpacks themselves, and can somehow deal the same amount of damage that the real one can. Definitely worse than the Prophet of Regret. If you're not careful, they'll shred you in the few seconds you have after the cutscene ends to get to cover.
** ''VideoGame/Halo5Guardians'': The Warden Eternal's bodies, who are even trickier to get rid of than [[BossInMooksClothing Hunters]]. Even on Normal difficulty, his various attacks (a rapid-fire eye beam, a powerful explosive orb that can penetrate light cover, and a dashing sword-swing with surprising range) will one-shot you, while he takes quite a bit of damage to bring down. On Legendary, he becomes a full-on DamageSpongeBoss, able to survive the emptying of an entire [[{{BFG}} power weapon]]'s magazine being emptied into him and keep coming for more, in addition to his aforementioned one-hit-kill attacks and [[FlunkyBoss horde of flunkies]] (who divide your attention, require more ammo usage to kill, and will be helping their boss kill you). [[spoiler:And toward the end of the game, Osiris' last encounter with him is against [[DualBoss two Wardens Eternal]] at once, while Blue Team fights ''three''.]]
* The Death Knight in ''Spear of Destiny'' is by far the most difficult boss in the game, packing more than ''twice'' the firepower of any other boss. To make matters worse, he's in a room with at least twenty mutants, guards, and SS in it, and no health or ammo. To replenish health and ammo, you have to run through this room and out a doorway, and into a ring-shaped corridor running around the level... which is full of officers. There is a better than even chance that you will die within seconds of entering the boss arena, before you can even get out into the outer ring and lure the boss into following you.
* In ''VideoGame/TimeSplittersFuturePerfect'', the Creature (Crow's monster) in the episode "Something to Crow About". The worst part is the collision detection for his body is wonky: So you step out from behind one of the ballroom pillars and open fire, hoping to take out one of his weapons. Even though it was a direct hit, the weapon didn't notice and is now unleashing hell in your direction, knocking you back into the proximity mines he laid, which blow you away from your cover so that you're now taking fire from multiple weapons. Rinse, repeat. And if you run out of ammo for both your minigun and your rocket launcher, you might as well put down your controller and wait for the boss to kill you, as nothing else you have is going to make a dent. Mercifully, there is a [[GoodBadBugs glitch]] that causes him to start the fight with zero health if the player skips the boss intro cutscene at the right moment (when the boss begins to raise his "arms").
* NME (or Nasty Metallic Enforcer) from ''VideoGame/RiseOfTheTriad'' is undoubtedly the hardest boss in the game (Yes, even harder than the final boss). Not only does the damn thing move very fast, but it also hurls mines and heat-seeking missiles at you. The developers ''outright state'' in the full-colour printed manual: "We even have trouble beating this guy." ''Extreme Rise of the Triad'' has levels where you fight NME in a small space. Good luck beating it in those levels.
* ''VideoGame/{{Killzone}} 2'', the first ATAC gunship fight (the second time it doesn't even really count as a boss fight). The ATAC is faster than Franchise/TheFlash on methamphetamines, has a fairly painful machine gun turret, and has rockets of +5. And your only source of cover in this fight is a single stone column in the middle of the area. Which offers you no protection at all from the splash damage of the ATAC's rockets, and is so thin that taking cover from the machine gun entails getting so close to the column that you ''can't see where the boss is.'' Basically, success in this battle comes down to getting in enough hits before the thing decides to spam its rockets and instakill you.

** The Siren is the only real boss fight in ''VideoGame/BioShockInfinite'', and it more than compensates. It doesn't have a lot of health but it's immune to most of your Vigors, and [[GoddamnedBoss constantly flits around the battlefield]] making keeping track of it - let alone actually ''hitting'' it - a minor miracle. It only stays still for a few seconds so it can [[FlunkyBoss resurrect corpses as enemies]]; they're not weak enough to just ignore, but by the time you've killed them The Siren will have gone to another group of corpses and resurrected them (and by the time you've killed ''them'' The Siren will have gone to the ''first'' group and resurrected them, ad infinitum). Using [[PlayingWithFire Devil's Kiss]] or [[ShockAndAwe Shock Jockey]] to disintegrate the corpses helps, but [[GoodBadBugs sometimes]] The Siren will just go ahead and resurrect that pile of ashes. The best part? You have to fight this monster ''three separate times''.
* In ''VideoGame/CliveBarkersUndying'', there's the penultimate boss, Bethany. She's widely considered to be much, much harder than the actual final boss, and has marked the point where many players have quit the game in frustration. For one thing, she flies, meaning that in order to get up close to her and perform the one melee attack that can kill her, you have to manage the awkward flying controls and fighting controls at the same time. Worse, she also summons enemies that can kill you in more or less one hit each and respawn endlessly, and who'll pile onto you, while she flies around overhead and you're trying to get to her to put a mercifully quick end to the battle. And since she's positioned right before the final boss, if you lose to it and quit the game, you will have to deal with her again.
* The Preacher fight from ''VideoGame/{{STALKER}}: Call of Pripyat''. After launching an elaborately planned ambush on a Monolith patrol, with sniper support and a squad of specially trained, heavily armored Spetsnaz, he announces his presence by instantly killing said sniper, and the ''real'' Monolith patrol shows up. Suddenly, you and your six man team are pinned down in the middle of an open courtyard, outnumbered nearly 3:1, with sniper fire raining down on you. Even worse, if you take too long the Preacher will start using the CoolButInefficient Gauss Rifle. Even ''worse'', even the best armor in the game will be instantly ruined by a single shot, and if you aren't wearing that armor, you die instantly. If he can't find you, he'll simply fire on your allies, and is capable of wiping out the entire squad singlehandedly in under fifteen seconds.
** Somehow, to make things even worse, in order to get a good ending, three specific Spetsnaz out of the six absolutely cannot be allowed to die. This doesn't sound like too huge a problem considering [[OneManArmy what you've been doing all game]], but two out of the three mission-critical guys are going to be out in the open when the Monolith guys show up. Even if you take out the Preacher immediately, you have to hope the ridiculously heavily armed mooks don't take down a single one of your important buddies. And if you take too long, one of the mooks will pick up his gun and use it on you.
** The game has another situation later in the game, during the final mission, [[spoiler:where you must escort a team of story-critical characters to the evacuation point]]. The catch? If you lost any men in the mission above, the survivors are weaker as a result. Half of them are outfitted with pitiful starting game gear. This EscortMission from hell gets even worse when another Preacher (using a powerful semiautomatic shotgun) appears at the very end (along with 40 more Monolith mooks!).

** The worse of these? '''Merasmus'''. He has so much health that the previous two bosses are made of glass in comparison. He also teleports a lot, will knock you a far ways away (if not outright kill you) with his staff, and loves spamming the fire launch attack. This attack knocks you in the air, lights you on fire, and for the first night of the update he would say a line that would make Robotnik proud ''every time he used it'' (Thankfully, more voice lines were added). He also will throw bombs, which deal a big chunk of damage and have no damage indicator (other than obviously losing damage or pain voice lines), so you don't know how much you're hurt until it's too late. Then he will teleport to the control point and rain the aformentioned bombs ''everywhere'' for about 8 seconds. So you've got him down to half-health. He then starts taking a strategy from [[GameMod Prophunt]] and spawns various props all over the map, one of which he's hiding in. These props take a surprisingly high amount of damage before being destroyed, and can hide in the most ''devious'' spots. And if you're not lucky... he'll do it ''again'' right before he's about to die. Randomly, your head might get turned into a bomb, which requires you to scramble at high speed without being able to jump or attack over to Merasmus so you can run into him and stun him; if you spawn in the prop-hunt stage, you're screwed. This is all compounded by the fact that he is only present for '''90 seconds'''. Combine that with his ludicrous health, and absolute team cooperation is not just neccessary, but ''absolutely vital'' to even get him down to half health. Even when nerfed some (he takes more damage from some classes), he's easily the most difficult Halloween Event boss so far. Bring the Huntsman; you'll need it.

*** The first Giant Heal-on-Kill Deflector Heavy on Empire Escalation (Operation Two Cities). It have '''70,000''' health, and can recover a staggering '''8,000+''' simply by killing just one player. If it kills enough, it can fully recover all it's health, even if it's at '''very''' low health, rendering the entire effort to take it down useless - and it has the ability to do so '''very''' easily. Let's just say it has every single benefit the Mecha Engine bosses had, without the restriction of loading. It is without a doubt the hardest boss in Mann vs. Machine. Thankfully, the other two only have 5,500 and 5,000 HP, respectively.

* The level 16 boss from ''VideoGame/{{Descent}} 2'', most commonly referred to as the "ice boss". He doesn't have as many hitpoints as the final boss and his weapons don't do as much damage, but he is armed with homing flash missiles that are nearly impossible to evade and will completely blind the player, making them a sitting duck for the boss and his minions to finish off. The typical strategy for defeating him involves a lot of tedious camping with guided missiles.
* ''VideoGame/{{Half Life|1}}'' has the Gonarch. It [[LightningBruiser deals brutal damage while still being faster than Gordon]], spawns [[GoddamnedBats baby headcrabs]] that are near impossible to ''see'' let alone hit, [[AttackItsWeakPoint can only be damaged if you hit it's colossal testicle]] (which is harder than it sounds given how much it moves around), and the battle arena is so precarious you're more likely to die by falling off rather than from its attacks. Worse, [[GiantSpaceFleaFromNowhere it comes from nowhere and has no relevance to anything]].
** The FanRemake ''VideoGame/BlackMesa'' has that damn helicopter in the cliff portion of "Surface Tension". It requires a ludicrous amount of rockets to destroy, will kill you in seconds if you're out in the open when it fires, and has a [[MacrossMissileMassacre rocket spam attack]] that can hit you behind cover if you aren't carefully positioned.
* ''VideoGame/NosferatuTheWrathOfMalachi'': The Draija Succubus, definitely. She has a lot more health than the other bosses and is very fast and manoeuvrable. But what really makes this fight unfair is the presence of a giant Portal in her room that spawns squads of Desmodiij to swarm you and takes a lot of hits to destroy, forcing you to divide your attention between targets, assuming you can avoid getting mauled by the mooks.
* [[VideoGame/{{Heretic}} Heretic's]] BigBad D'Sparil is annoying enough on Smite Meister (Hard), but on [[HarderThanHard "Black plague possesses thee"]], D'Sparil teleports around the arena so much that you may wonder why he doesn't just teleport out of the level and run away. On top of his infuriating TeleportSpam, he summons his flying disciples to fight by his side, and keeps summoning them without limit. It is very easy to lose the fight because you got overwhelmed by his followers.
* The first boss of VideoGame/{{Painkiller}} also has the benefit of being the hardest, due to a [[OneHitKO certain death]] [[ThatOneAttack attack]] that literally covers the entire map save for four small phone booth-size cover areas spread about 200 feet apart. And it isn't telegraphed.
* The German sniper in the mission "Vendetta" in ''[[VideoGame/CallOfDutyWorldAtWar Call of Duty: World at War]]''. [[SniperDuel You have to use a sniper rifle to take out an enemy sniper in another building, while he is trying to do the exact same thing to you]]. He always knows where you are, but you have to track him across a number of windows. On the highest difficulty, you have to hit him ''three'' times before he dies (with the stupidly flimsy excuse that you've only grazed/wounded him) which makes it absolutely insane since he can [[OneHitKO kill you instantly]].

** In ''VideoGame/{{Halo 2}}'', the Heretic Leader, particularly on the HarderThanHard Legendary difficulty. Equipped with a jetpack, near-instant-death dual Plasma Rifles, and multiple [[DoppelgangerAttack holographic doppelgangers]], all of which have jetpacks themselves, and can somehow deal the same amount of damage that the real one can. Definitely worse than the Prophet of Regret.

* Packrat Palooka from ''VideoGame/{{Oddworld}}: Stranger's Wrath'', who is essentially an [[KingMook upgraded version]] of a rocket-firing outlaw. Most of your sucess depends on you managing to knock him off of his platform with Boombats or [=ThudSlugs=], and then giving him a good arse-kicking before he scrambles back up. ''All whilst he continually fires homing rockets at you, which can kill you in just a few shots''. And that's not even getting into trying to capture him ''alive''.