MMORPGs have an unfortunate habit of sending players after these sorts of bad guys, especially for Raid encounters. Especially painful when pausing hurts the team.
The all-time god-king of this trope is Pandemonium Warden of Final Fantasy XI. Absolute Virtue may be practically invincible, but 18 hours, and the Warden still isn't dead? Makes one wonder if the developers like leather and pain. Square Enix has changed things in response to the bad press about Pandemonium Warden so that both it and Absolute Virtue are weakened and will vanish after two hours of fighting. However, while the new PW isn't unreasonable to beat within the alloted time, AV remains unbeaten without cheating. SE seems to be fond of the Guide Dang ItPuzzle Boss, except without the "guide" part. Square-Enix seemed determined to make the guy literally unbeatable for a long while. Every time a group managed to defeat him, often through "creative" use of mechanics, SE claimed that the method they used was "improper" and then patched him to cover that weakness. Even a strategy that Square-Enix themselves used to beat him, and subsequently published in a video, was later patched.
City of Heroes and City of Villains mostly avoids this, but the old version of Hamidon could take three hours even with a large raid and smart players. Nowadays people have gotten him down to 15 minutes.
The last mission of the Imperious Task Force can go this way, with the Nictus-infused Romulus having three 'pet' Nictus Essences that deliver additional damage, one of whom also has an area-of-effect heal (on top of Romulus' own impressive healing rate) whose effect increases for each player character within a fairly long radius, often making this fight a protracted and painful process.
World of Warcraft. Early Molten Core raids regularly spent an hour or so on the earlier bosses.
Take Kael'Thas Sunstrider, for instance. In his first phase, he sends his four minions at you one at a time. Then you fight magical moving weaponry for phase two. When those go down you you fight all four of the minions at once after he... had a soulstone on them or something. Phase four he finally attacks you. In phase five, he adds a couple neat tricks. Did I mention he talks for about ten minutes at the start, each of the mini bosses have their own line when they attack/die and there's a speech between every phase? Plus after this there's Magister's Terrace because he was empowered by a demon lord. This weakened him into a five man where he continued to talk you to death. People literally lost the fight because they stopped paying attention during his speeches only to find out the fight had started.
General Rajaxx and co in Ahn'Qiraj will send waves of his mooks and Quirky Miniboss Squad before you fight him.
For that matter, every boss except Archimonde in Mount Hyjal, because you needed to kill eight waves of mooks before the boss even showed up. Fighting Illidan in Black Temple also takes around 15 minutes, when other bosses in the Black Temple take around three minutes each.
There's also Deathwing, the Big Bad of Cataclysm on heroic. You first have to actually get to him while his Mooks, which include a boss battle fight you on the way there, which may or may not count, then you fight him. He's two individual boss battles. First you have to kill all but 2 of the tentacles on his back, which start at 4, then get him to flip over, killing the Elite Mooks that spawn, then you kill the last tentacle, kite the mook around killing lesser mooks while whittling it's hp to 10% or so while pulling him over all the dead lesser mooks, to make him unstable, exploding and revealing the actual weak point which is then attacked, it takes 2 tries to kill, so now you take out his final tentacle and repeat the explosion part all over again. If you done all that, Congratulations! There are now six tentacles and you have to repeat it again, then one last time with eight. After that's all done, you have beaten the first boss battle with him. The second involves killing a large tentacle so it doesn't use it's Impale twice which deals Massive Damage, then killing his arm, which is clinging to the platform, which spawns waves of mooks that deal escalating damage once again forcing you to kill them, all while deathwing occasionally blasts you with a big rock that deals a chunk of damage, then constantly deals damage, forcing you to kill that. If you don't do all of this in short enough time, he finishes casting "Final Cataclysm" causing a Nonstandard Game Over. Done? Good! You lose one of the 4 buffs and have to do it 3 more times. THEN comes the final bit, where he spawns unending waves of mooks, and does damage to everyone based on how much hp he is missing.
EverQuest has more than its share of Marathon Bosses, although some of them, such as the Sleeper, probably weren't supposed to be killed. Kerafyrm, AKA "The Sleeper" was intentionally designed to be unkillable. What is suppose to happen when you wake him up is that he goes on a rampage through various zones on the continent, getting his revenge against dragon-kind for putting him to sleep in the first place, and then disappearing forever. A ONE-TIME ONLY event for the entire server. After it happens, that's it, it will never happen again. The top three most powerful guilds on the Rallos Zek server took this as a challenge. Using Zerg Rush tactics to keep Kerafyrm distracted was the only way they could fight him, because he hit far too hard to properly tank him. On top of this, he was completely immune to all spell attacks except for the Shadowknight's Harm Touch and the Wizard's Manaburn, both which can only be used once every 90 minutes, and could only take hold once every minute on Kerafyrm himself. Nearly 300 players took roughly 3 hours to finally whittle him down to zero. His corpse had no loot.
The difference between the real bosses and the smaller "Area Bosses" in MapleStory is that the real bosses take upwards of two hours to kill with a full party of overleveled characters while the Area Bosses go down in less than two or three minutes if they don't kill you first.
This is actually a built in mechanic for the Player Owned Station's in EVE Online. Which have incredibly staggering amounts of hitpoints, the larger stations tended to have so much, that they required dedicated ships whose sole purpose was to function as siege tanks against these shields, whom deployed specialized heavy caliber weapons that could only be realistically used against these shields, with a unique module that assisted in doing so. And it still took hours if not more then a day, with multiple units, just to collapse these shields. Justified in the fact that this was to allow the owners of the station time to mount a counterattack before the station could be taken down.
Additionally, most of the higher end Sleeper drones in the more dangerous wormholes have incredibly high amounts of hitpoints and do staggering amounts of damage. So that even super carriers can't solo them.
Guild Wars 2 has several world bosses with 15-30 minute timers before the event fails, while failure to kill them before that will typically yield little or no reward.
The Claw of Jormag fight typically has six stages where it is impossible to directly damage the boss, forcing the players to instead deal with hordes of adds, protect friendly NPCs, and tear down ice structures. These stages can easily last several minutes each, while the boss itself can be damaged for less than a minute at a time between them. The total allowed time for the fight is 30 minutes.
Tequatl's battle has the boss depart the arena every 25% of his health bar, stopping the timer while another event plays out. If successful, Tequatl takes damage and the standard fight resumes. The boss encounter has a maximum length of 15 minutes, but the events raise it to a possible 21 minutes for a full-length fight.
The Prime Hologram during the Battle of Lion's Arch was a three-stage fight with a maximum time limit of 25 minutes. Successful fights typically ran 20 to 22 minutes. Unlike other bosses where downed players could run back, the Hologram arena could not be entered after the battle started, requiring those inside to resurrect others as well.
Fighting the more powerful dragons in The Last Remnant with an extremely underpowered team can take over 40 minutes. This is more due to being able to defeat strong bosses with a weak team with good tactics (heal spamming), than the boss itself having high hp. Basically, the dragons will take out around half your team each hit, meaning each party member spents 99% of their time either dead or reviving other party members, and 1% of their time actually attacking the dragon, for a pitiful amount of scratch damage.
The Emperor Bulblax in the first game has a buffed life meter that takes much longer than any other creature to go down.
If you're playing cautious with your Pikmin, the Titan Dweevil in the second game can go on for somewhere around 45 minutes. The reason is because all of its attached objects have to be disabled one by one, and each a high amount of hit points has to be inflicted. Combined with the life meter of the Titan Dweevil itself, this boss has the highest HP of any boss in the entire series. This trope can also happen with some of the more powerful bosses, such as the Pileated Snagret and Man-at-Legs.
The third game's Plasm Wraith continues the tradition of long-lasting final bosses. Before you even actually fight it, you're forced to go through the longest Escort Mission in the game. Once the actual fight begins, you'll very quickly discover that the boss has a very highamount of health, only topped by the aforementioned Titan Dweevil. In fact, it's so much of an Implacable Man, that you don't actually kill it.
Among the bosses of the Arachnorb family, the Shaggy Long Legs in the third takes the longest to defeat because the player has to unveil the weak point first, and for that all eight knots of hair (located in the legs) have to be dealt with. It doesn't help that the boss has a bad habit of moving from one place to another, forcing the captains to either go on foot to the proper destination to resume the fight, or split up to intercept the boss (which itself is risky if one of the captains is currently low on Pikmin).
Dragon Quest VIII features a Final Boss where before you could even attack, you had to use a special item seven times by all four party members. Moreover, you're being attacked the whole time, and pretty much have to heal every other turn. Then comes the absurdly large health meter - and this boss has a habit of healing himself regularly, stretching it out even further.
Dragon Quest IV does this. Necrosaro/Psaro the Manslayer refuses to die. He will transform six times for a whopping seven forms. His fourth form, the one where he finally gets serious, has the most HP and he constantly spams a healing technique. Dragon Quest IV's final fight can be boiled down to whether he runs out of HP before your healers run out of MP. And in the original NES version, where you're stuck with AI control for everyone except the main character, luck is an even bigger factor than usual for boss fights. As in, "will I luck out and have my healers actually heal when I need them to?"
The final boss of The Wonderful 101, when considering the entire stage. Each individual phase isn't that long, but all together it takes about half an hour to beat him, and that's the Platinum time!
The Negativitron of LittleBIGPlanet 2, who can only be hit at certain intervals of the fight, and all you can do is attempt to survive in between phases. Beating him can be very stressful as you get low on lives, but acing the fight (that is, beating him without a single death) is the real nightmare.
Pyribbit in Kirby Triple Deluxe, as he starts to spend a lot of time in the background during the second phase and spends very little time vulnerable with he does show up to be hit. If you take a hit during that time (and you likely will, as every time he comes back to Kirby's platform, it's accompanied by an attack) and spend most of it stunned, the fight will only take longer. Made even worse in Dedede Tour, where you not only have to fight Pyribbit EX, but you have to be quick about it, too.
Dragon Ball Z: Gokuu Gekitouden has Frieza as this, of the series of somewhat smaller fights variety. His first form has 200,000 life, and each form after that has even more. The basic outline of the fight is: You fight Frieza's first form (200,000 life) using Gohan, Krillin, and Vegete. Then when you beat him he transforms into his second form, which has 300,000 life and you continue to fight him until Piccolo shows up. Then Piccolo goes one-on-one with Frieza's second form and when Frieza loses again he transforms into his third form, which has 350,000 life. Once Frieza has transformed into his third form Vegeta, Gohan and Krillin join in to help Piccolo, and once Frieza loses AGAIN he transforms into his final form, which has 400,000 life, and you fight him until Goku arrives. Then Goku goes one-on-one with final form Frieza and drops a Spirit Bomb on him when you win. And then, if you meet the requirements for the True Ending, Goku goes Super Saiyan and fights 100% Final Form Frieza. Twice. This whole sequence of bossfights takes no less than three hours. And you can't pause during battle. Fortunately the game is generous enough to allow you to save in the middle of this series of bossfights, once when Piccolo arrives and again when Goku arrives.
Elizabeth Greene in Prototype. Depending on how you've set up Alex and how you use artillery, tanks, and helicopters, you can potentially take down Greene in, oh, say, fifteen minutes of continuous pounding.
The first form from the eponymous final boss of the first Metroid Prime game is very much this. The battle itself really isn't too hard, but it takes forever. Even your most powerful weapons, like the Ice Spreader, do only minor damage to it, and a lot of times miss and hit his impervious lower body. Nothing says "screw you" like wasting ten good missiles to hit him with an Ice Spreader, only for it to bounce off.
A lot of bosses in Metroid Prime 2 are given ridiculous longevity (large amounts of HP and multiple phases), as well as the fun bonus of them being Puzzle Bosses. Adding to it is that most of them are fought in an environment that constantly drains your energy. Note that they are long battles by action game standards, as they are still much shorter than many other of the examples in this page. Special mention goes to the final bosses. The first one has multiple phases, all of which are long endurance matches (there was an additional phase that was Dummied Out). Meanwhile, the second is timed and you have to use an almost Guide Dang It-y trick to beat it; fortunately, losing just causes you to go back to the beginning of the second boss.
Also in Prime 2, Chykka takes a particularly long time. Dark World boss fights do have the light crystals, which slowly heal you, so they might have felt justified in that you have a theoretically infinite supply of health.
Mogenar from Metroid Prime 3 takes long if you don't know how to beat him. If you try to use the wrong strategy, prepare to try to fight is regeneration. However, if you attack him the right way (and are quick), his regeneration doesn't even factor into it.
Want to take over Earth, Luna, Stardock Alpha or Ruby in Escape Velocity? Demanding tribute from any one of those will force you to gradually work your way through the several thousand ships in its defense fleet. Or Omm in Override. For a planet of worm eating pacifist monks, they have a surprisingly large defence force. Council isn't even worth trying.
And of course, Metal Gear Solid 3: Snake Eater has The End, a sniper battle that can easily take an hour or more if you don't kill him via Easter Egg (by sniping him long before the battle starts, or by waiting a real-time week for him to die of old age.) As a webcomic said it... "Hey, you wanna have a 45-minutes sniper fight?"
The fight with The Sorrow can easily become one if you've been playing aggressively so far, and you don't know (or don't use) the quick way.
Metal Gear Solid 2: Sons of Liberty's penultimate boss fight, Metal Gear RAY. On the easiest difficulty setting, you only have to defeat three of them and they can be killed in five hits maximum. On the hardest two, you have to defeat twenty of them, and they all have masses of HP.
In Metal Gear Solid: Peace Walker, the second Peace Walker fight can easily be one of these in single-player mode. She has massive amounts of HP, a weak point which she often moves around making it difficult to hit her, various attacks which can freeze you or knock you over, and an ability which makes rocket weapons useless for about two minutes. She also regularly takes cover behind some buildings you can't follow her to. And you have limited ammo.
The final boss in Final Fantasy II, if you played the game normally (i.e not maxing out evasion, wearing armor, and not getting the blood sword). To put things in perspective, a party that has done an average amount of grinding will do about 300 damage per attack on the final boss, who has 15,000 hp and constantly heals itself for roughly 5,000 hp every time he uses a physical attacks. Players who didn't utilize a Game Breaker at some point will probably spend about four hours fighting the final boss.
The final battle will Kefka has four phases, all with much damage necessary.
Then the Game Boy Advance version added two Bonus Boss examples only for hardcore players. The Kaiser Dragon has 327,500 HP, which is about two hours of fighting, not counting time spent healing. And Omega Weapon, who has the same amount of HP as Kaiser, but dualcasts Heartless Angel and Delta Attack, which results in your entire party dying, regardless of level.
Bonus Bosses Ruby and Emerald Weapons. Emerald Weapon is a particularly cruel case in that the game gives you a 20-minute time limit to beat it, unless one of the characters is equipped with a stupidly obscure piece of materia, which is more or less mandatory if you don't have a special strategy in mind.
There's also Sephiroth, the Final Boss. If you play through normally and don't grind for experience, the battle is about the length that you'd expect. However, reaching level 99 is a curse rather than a blessing, for Sephiroth's HP is proportional to your level, meaning he'll end up with an obscene pool of damage (even more if you used the Knights of the Round summon before fighting him). Sephiroth can end up with 400,000 HP and obscene defensive/attacking stats, meaning you'll be fighting him for quite a while.
Ultimecia . There are two abilities that can break the standard cap of 9999 damage, and both are fairly hard to get, so you'll probably be damaging at or below that cap with every attack. The "Regen" spell heals you by a small amount every once in a while, apparently a set fraction of your maximum health. When you cast Regen on yourself with a maximum health of 9999 HP, that being another cap, the healing is still in the double digits. If Ultimecia's second form casts Regen, it'll heal itself in the high quadruple digits. Ultimecia has four forms. Have "fun."
And if only junctioned your main party members, and one dies. Have fun fighting all four forms with only two useful party members.
By her fourth form, it gets even worse as she can "blow" away junctions. If the battle ends up taking too long, you'll end up with miniscule stats and hp because the final boss took away all your junctions, and if this happens, you will lose and have to lose the past hour's worth of work.
Nemesis, the ultimate Monster Arena opponent, has 10 million HP. Many of the other creations may count too, depending on your level.
Many of the Dark Aeons and the mother of all bonus bosses, Penance, from Final Fantasy X International. The weakest of the Dark Aeons has around 1 million HP. Dark Anima has 8 million HP (the highest of the Dark Aeons). Penance tops that with 12 million HP. And unlike some of the marathon bosses, all of them are hard. This Youtube video of the Penance fight: just under 49 Minutes.
Yiazmat, the ultimate Bonus Boss shown in the picture above, regularly takes players as much as 12 hours to kill, thanks to its astronomical 50 million HP. You're allowed to leave and come back, though. The Internationalversion nerfs him a bit by making him vulnerable to the four "Break" abilities, allowing you to greatly reduce his stats. Combine that with the fact that the damage cap is removed (so you can do more than 9999 damage per attack) and he goes down much easier. The real kicker? Near the end of the fight, Yiazmat pulls off a little trick that, if not caught and stopped, heals him back to full health.
If you fight Zodiark as soon as you can (after beating Giruvegan, but before you can buy the spell Scathe), and aren't at a high enough level to slice off his last 50,000 or so HP before he puts up a Paling, expect to spend at least half an hour taking off the last of his HP bit by bit with non-elemental magic spells such as Scourge or Drain.
Vercingetorix, who has 15.8 million HP (although it's worth noting that the default damage cap in that game is 99,999, not 9,999, and the fight will probably take no more than 15-20 minutes).
Some of the oretoises. An Adamantoise has loads of HP and its resistances mean you only do 10% of normal damage (1% of normal with any elemental attack.), although those resistances can be lowered by attacking its legs, which renders it briefly helpless and vulnerable. The target time for killing one is around 30 minutes (although a high-level party can potentially win in 2-3). The good news is that they're susceptible to Death, so with a little luck or a lot of patience the fight can be very short. Long Gui (the more powerful version of Adamantoise), however, are not vulnerable to Death.
The Final Boss, Garnet/Amber/Jet Bahamut. Garnet and Amber hang on to the side of the platform you're on and smack your party with powerful attacks, while Jet hovers a ways off and buffs Garnet and Amber. When you take down Garnet and Amber, who both have over 100,000 HP, Jet comes forth and challenges you. Jet has over a million HP, and gives you only a brief window of time to attack him before he revives Garnet and Amber, forcing you to take them down again. Also, after you start doing some serious damage to Jet, he starts using combination Flare attacks with Garnet and Amber, the strongest of which can easily wipe all but the most powerful of parties.
Not present in the original Dissidia: Final Fantasy, but there in the prequel, Duodecim. The version of Feral Chaos one must beat to unlock him as a playable character is, in addition to being at level 130 when the player is capped at 100, in possession of a stunning 125,000+ HP. In the Dissidia combat system, the most damage that can be done at one time is 9999—but, given the way combat works, the player will only be able to pull off a 9999 damage hit rarely if at all against the boss, with hits in 500-1200HP damage range being far more likely. This, plus the fact that the player will be performing Bravery attacks in addition to HP attacks, plus the fact that the player is going to spend a loooot of time trying to avoid the boss's utterly devastating attacks, given that the player is likely to have only somewhere in the realm of 10K HP and basically has little-to-no healing...essentially, it adds up to a very long fight.
While the boss is certainly intended to be a monster who takes a monstrously long time to beat, there have been reports of people manipulating the game mechanics (and not by cheating or hacking) to knock out all of the boss's HP in less than five minutes.
The Computer Virus is this in general in the Arenas of Kirby Super Star. The Arenas are, by nature, about getting a good time, and the format of the Computer Virus battle seems to exist solely to slow you down. In Helper To Hero, some abilities are affected worse than others by it. Special mention goes to Knuckle Joe, who cannot deal enough damage in one go to defeat the Computer Virus with anything resembling quickness. Oftentimes, the Computer Virus battle can make up a solid 1/4 to 1/2 of a Knuckle Joe run.
The main series Pokémon games each end with the Pokemon League, a series of battles against the regional Elite Four and the Champion. While you can save and use items in between each fight, you don't have access to a Pokemon Center, and losing any of the fights forces you to challenge them all over again. Starting in Black and White, you can choose which order to fight the Elite Four in to take advantage of Elemental Rock-Paper-Scissors, but the Champion always comes last, and they always have higher-level Pokemon as well as a team made up of multiple types or with good coverage.
Pokemon Black and White does it slightly differently. After beating the Elite Four, Team Plasma's castle appears, and you fight three more bosses: Reshiram/Zekrom depending on version (you're also forced to catch them, dragging out the battle even longer), N, and then Ghetsis. You're healed in between each of the fights though, so it's not quite as bad. Subsequent runs of the Pokemon League let you challenge the Champion, but both him and the Elite Four have much tougher teams.
The Legendary Pokemon fights count as this as well, especially if you're trying to catch them: every legendary has an exceptionally low catch rate, forcing you to waste tons of Ultra/Dusk/Timer Balls (or just get extremely lucky). You can avoid this with a Master Ball, though you usually only get one per game, and they really should be used on Roaming Legendaries.
The final bosses of both GBA Golden Sun games. The first game's final boss is also a Sequential Boss (and its first form being a Dual Boss). Many of Golden Sun: The Lost Age's Bonus Bosses also qualify, most notably the Star Magician. The Dullahan can be, because it's a Puzzle Boss (unless you're massively overleveled) with attacks capable of screwing up your strategy.
Guess who got an upgrade for his return in the bonus dungeon of Dark Dawn?
For the first Golden Sun, there was Deadbeard, who was considerably harder than the final boss because of the fact that he resided in the biggest, hardest dungeon in the game.
The final boss of The Lost Age actually has multiple forms/HP meters, though they're not shown. In addition to the obvious issues of this trope, every other boss in the game can easily be bum-rushed with Summon Magic, and many players learn the hard way that trying to summon-rush the Doom Dragon only takes out the first, most harmless head, leaving them without defenses when the remaining heads start spamming Cruel Ruin and Djinn Storm.
The level 7 boss and the Final Boss of the original Descent both took absurd amounts of damage before dying and would take you from full health to nearly dead with one missile. In fact, if you don't apply a patch, the final boss is actually invincible on all but the two easiest difficulty levels, making the game Unwinnable. Said patch also makes the level 7 boss die much more quickly.
Dungeon Siege II has a number of these bosses: with the black mage battles, you must destroy 3 crystal prisms that form an impenetrable shield around the boss before you can do any damage; you are then allowed to take away about a sixteenth of their health before the crystal prisms return.
The Sa-Matra in Star Control 2. First you have to fight through a bunch of Ur Quan dreadnaughts before taking out all of the Sa-Matra's shields and then piloting a bomb into the Sa-Matra itself. And to make matters worse, the most effective strategy is to use Pkunk ships, a Fragile Speedster with only a weak, short range weapon.
Fullmetal Alchemist and the Broken Angel: Practically every boss fight is like this, especially the endgame, where you have to fight THREE giant chimeras at the same time, one of which heals itself, then fight two more bosses with no refuel. And then two more bosses. While winning the last one is optional, it makes it pretty damn hard to achieve 100% Completion. This optional fight is against [[spoiler:Colonel Mustang and Major Armstrong simultaneously. They have 6999 and 9999 health respectively, and your regular attacks do one damage per hit.Death of a Thousand Cuts indeed. The kicker? You need to do this fight twice to get 100% completion, because the fight ends before you can grab the item drop from whichever one you beat second.
Shin Megami Tensei III: Nocturne has Noah who likes to change what he takes damage from and is one of the few things resistant to almighty spells so if you don't have demons with multiple elemental attacks you will have a long ass battle, and even if you do its still going to take awhile.
Shin Megami Tensei IV has the DLCBonus Bosses Ancient of Days and Sanat Kumaya. The former especially, as it has Diarahan and will spam it frequently (this pretty much forces you to get another'' DLC that provides the only source of the Brand ability other than Ancient of Days himself). The third DLC Bonus Boss, Masakado's Shadow, would be this if not for the fact that it has a turn limit, especially since it doesn't hit terribly hard compared to the other two.
Digital Devil Saga: While he doesn't take as long as some of these other examples Hitoshura himself takes around 30 minutes to beat at least. It doesn't help that he is extremely difficult where, if you are unlucky, you can wipe at any time (and not from Gaea Rage)
Diablo himself in Diablo II, who not only has a ton of HP, but most certainly is a threat. You'll spend a lot of time attacking and a lot of time dying.
Mega Man 9 plays with this trope. One of the achievements there can be gotten only after fighting a boss for at least 10 minutes and winning.
All of Monster Hunter. It's a Boss Game so almost every mission is just a boss fight. While the earlier ones can take 10-15 minutes, the end game bosses can take up to 45 minutes, and some of these are even with four hunters hitting it. Keep in mind that most fights have a time limit of 55 minutes so it's EXPECTED to take that long.
The Elder Dragons s. Their Armor is extreme and the huge ones (i.e Ceadeus, Jhen Mohran, and Lao-Shan-Lung) have extreme hp and take at least 30 minutes or more. And most of the time they have a SMALLER TIME LIMIT than standard.
Any monster that takes a long time to kill will just be a nightmare when you have to fight more than one at the same time.
The True Final Boss, Henry, on Bitter difficulty, can take nearly a thousand hits before dying. You generally can do less than ten hits off a dark step (the timing for which is tighter in this fight than in any other in the game). Trying to exploit his normal openings will land you maybe three hits at a time, and a high chance of getting countered by something nasty.
The normal final boss, Jeane, also takes a very long time to wear down, especially on Bitter difficulty.
The Bonus Boss in Shadow Hearts that is required for the Good Ending is a real grind. It's not particularly challenging, as its attacks don't vary much, but the fact that you have to fight it with only one character, who takes all the damage and has to do all his own healing, can make the fight last half an hour or more.
In Rock Band and Guitar Hero, while the time needed to beat them may pale in comparison to some other examples on this page, any song that reaches over eight minutes or so becomes one of these. "Do You Feel Like We Do" (Live) from Guitar Hero 5 pushes it even further with almost fourteen minutes of playing.
Also, the Endless Setlist challenges in the numbered titles are guaranteed to take over an hour. Subverted slightly in that you can pause in the middle of any song... unless, of course, you want that Steel Bladder achievement, in which case you have to never pause the game and never fail a song during the entire setlist.
In Rock Band, the Endless Setlist challenges will take (on average) 5+ hours. The challenge itself is to play the entire game's tracklist in one concert. 84 songs x 3(on average though usually higher) minutes, = approximately 300 minutes, or 5 hours.
Another example is Metallica's "One", which, while only just short of 8 minutes, starts with a 30-second intro of absolutely no playing. Seeing as the song waits until the five-minute mark before trying to wear you down with a carpal tunnel-inducing riff, and then a minute later unleashes a sudden, difficult solo that can crush you in seconds, you'll likely be wasting far more time trying to beat it than you should.
Fallout 3 has this in some of the expansion packs, although with new high level creatures rather than bosses, such as Super Mutant Overlords and Feral Ghoul Reavers, both of which can take several dozen shots to the head from the strongest weapons in the game and not flinch. The Super Mutant Behemoths can also take a long time to wear down if you aren't equipped with a Fat Man.
Fallout: New Vegas: Old World Blues has the Legendary Bloatfly, which has the HP of a Super Mutant Behemoth and spits One-Hit Kill plasma, and the X-42 Giant Robo Scorpion, which can have up to 3500 HP, the highest of all creatures in the series, and a damage threshold of 30, plus a Wave Motion Gun on its stinger.
Lonesome Road's Big Bad Ulysses has the highest HP of any humanoid character, and is assisted by a pair of respawning Eyebots that restore his HP and repair his equipment.
In Star Ocean: Till the End of Time, Freya becomes an optional boss you can fight after completing the main game. She has 20 million HP (and that's just on easy mode!) and her attacks, namely EtherStrike, can kill even the highest leveled characters in one or two hits. To even have a tiny hope of winning, your team must be maxed out to level 255 and be equipped with the strongest weapons and accessories that can be found in the game. You must also have a whole inventory's worth of bombs, so that you can hopefully interrupt her attacks by blowing her up.
Her predecessors The Celestial Queen and Lenneth, while not even possessing a fraction of her power can drag on for an eternity. Raise Fayt's defense to the point that he takes zero damage from their attacks, and the fight still drags on for on the upper echelon of 45 minutes. Ridiculous doesn't even begin to describe Star Ocean: Till the End of Time's Bonus Bosses.
Of the six bosses in Iji, three could be easily said to be marathon bosses, especially on higher difficulty levels; worse still is the fact that they're Puzzle Bosses who you're supposed to damage with either the arena or by reflecting one of their attacks, which serves to make the fights very repetitive.
Even better: any atempt to defeat the Sentinel -without- using the power fields (something you have to do if you want to get 100%), or Tor later on with Maximum Charge, on Ultimortal, will effectively take you upwards of ten minutes - and that's if you're lucky/skilled enough to beat them within that time frame. To put it into perspective, the maker of this game takes more than seven minutes to put the second one down!
Perfect Cherry Blossom has Yukari Yakumo, who takes over 10 minutes to defeat, and over 15 minutes if you try to time out her attacks (say, to graze for score). Many shmups take about 20-30 minutes to complete, total. And to even get to Yukari, you have to beat the Extra boss Ran Yakumo. Twice. You see, Yukari's not PCB's Extra boss. She's the Phantasm boss. No other Touhou game has a Phantasm stage.
In general, every Extra boss in the Touhou series is relatively guilty of this. The only thing that really puts Yukari in a league of her own is her final card/attack, Danmaku Bounded Field. She's invincible during the whole thing, and it lasts for a minute and a half. Have fun. The timer for her last card stops any time you die or bomb until your invincibility wears off, unlike every other time-out card in the entire series. Have fun, indeed.
Typically the last spellcard in any game is absurdly long. The average spellcard lasts about 15-20 seconds, 45 if you're going for the timeout. Final spellcards can last two and a half minutes.Kanako Yasaka's final card is particularly terrifying. Once again, Yukari takes the cake. Her optionalLast Word spellcard in Imperishable Night is an extended version of the aforementioned last spellcard in PCB. Except you're not even allowed to bomb at all.
Since the .hack// games try to emulate an MMO, they had to include a couple of these bosses. For instance: most of the Phases, in particular Macha, Corbenik (both from Volume 4), and Skeith (from Volume 1), the last of which is the hardest boss in the series, and especially the final Cubia fight, in which you fight your way through three of his "Cores", with each having more health than the last. Then you get to fight Cubia proper... and he fully regenerates his health once you kill him. So you get to kill him again... and then he regenerates again, at which point the plot takes over and he's killed in a different way.
Phantamanta from Super Mario Sunshine provides one of the longest boss battles in the Mario series due to being an Asteroids Monster. It starts as a big, phantom-like manta ray, and can split into up to 64 smaller rays, which spread across the coast of Sirena Beach as they spill electric goo; this forces the player to both clean up the mess and eliminate the rays one by one.
Bonetail from Paper Mario: The Thousand-Year Door. It has a grand total of 200 HP, which is 50 more than the final boss (both actually being big numbers in this game). It will prolong the fights by causing Confusion and healing itself for 20-30 HP per heal, amongst other things. Woe be you if it defeats you after you trekked down all 100 floors to get to it.
Culex from Super Mario RPG, with his four Crystals and a total of over 12,000 HP between the five (with Culex himself having the most). Though you can speed things up a little by focusing your attacks on Culex, that means you'll have to endure the bombardment from him and the Crystals. It's a long fight no matter how you approach it.
Dreamy Bowser from Mario & Luigi: Dream Team heals a lot (and can't be attacked while doing so, as you have to defeat his Mooks first), which can stretch the final battle out for over an hour, especially on Hard mode.
Amaltea, the Guild Quest Bonus Boss from Arc Rise Fantasia: High HP, multiple layers of defense against magic, physical, and Excels(single, Trinity Acts, and Excel Trinities).
Luca Blight, from Suikoden II. You have three fights in a row against him (each time with 6 different characters), in which he may or may not kick everyone's behinds before proceeding to the next one. Depending on your teams, each battle can take up to 10 to 15 minutes each, though it should be noted that the first two battles will end early if your teams manage to do enough damage to him, and that if said teams do their job well the last one will be able to beat him rather quickly. On the other hand, if your first two teams don't manage to weaken him at all, the last one will have a very long battle on its hands, and it's not guaranted that Riou will be able to keep everyone alive until he's defeated because of his limited usage of the Bright Shield Rune. And after all that you get to run after a fleeing Blight, fight a few mooks, and finally you kill him... after a one on one duel in which he may OHKO you if you pick a single command wrongnote During the Duel, you can see his life bar, showing how much life he has remaining after getting thrashed by 18 extremely powerful people: a quarter. He literally has more HP than all the rest of your 108 party memebers combined. You can't save between fights either. To this day, this fight remains the most challenging one of the entire series.
Reflux, the final boss of Rayman 3: Hoodlum Havoc, goes through several phases and can take over an hour to defeat.
Spoofed in Kingdom of Loathing, where the final battle actually doesn't take all that long, but the dialogue at the start of the third form claims it is:
"Dang it!" you shout. "How many times do I have to kill you? This battle has taken over a half an hour and there's no save point!"
Spoofed again with Ed the Undying, whom you have to fight seven times, dismembering him into progressively smaller collections of limbs (and halving his maximum hit points each time). You eventually sweep his remains into the corner while he's still taunting you.
Bosses in the first two Ys games get most of their difficulty from this trope. In the first game, you're evidently supposed to fight the final boss at level 24 (that being the Cap in the original PC-88 version and the remake), but walkthroughs for the TurboGrafx-16 version generally recommend level 40 so you're killing him by a method other than Death of a Thousand Cuts. It's a bit harder to tell what level you're supposed to be at for the second game's fights, but killing every Mook you see, then consistently hitting the boss with fully powered-up attacks, leaves you doing so little damage that you need to hit the bosses twice to even notice a change in their screen-spanning life bars.
Darm in II is also a really long boss fight, even with your EXP maxed out. Then there's his teleport spamming and the constant rain of fireballs you must dodge.
Arem, the Big Bad of Ys IV: The Dawn of Ys, takes it Up to Eleven. He has three lifebars(the last form fortunately is a Clipped Wing Angel), a laundry list of powerful attacks, is hard to hit, your attacks only do miniscule damage even with max EXP, and he can regenerate his HP.
Some of the later bosses in the Nintendo DS FPS Moon can take 192 bullets from your rifle (that being the maximum you can carry) and still be less than halfway to dead. Matters are exacerbated by the fact that sniper rifle ammunition is rare and the pistol's hard to use while dodging, so you'll be using your assault rifle for the rest of the fight, which damages bosses so little that only on the rare occasions they stop shooting at you temporarily will you be able to see their health bars going down as you pump them full of lead. Dying and retrying four or five times can lead to physical pain in one's left hand (that being the one in charge of holding down the L button to rapid-fire.)
Devil Survivor: Belberith is pretty nasty, forcing you to walk all over the map before you can hurt him, all the while attacking you and summoning enemies. And when you finally get in range to hurt him he has tonnes of HP, nasty resistances, and regeneration. And he pales in comparison to the final boss. If you're playing Amane or Naoya's path it merely involves taking down a boss while enemies are spawning, taking out all of the Bels, including Belberith, and then killing the supremely nasty Babel. If you're on Gin or Atsuro's path it's longer and even nastier (though not including the Bels). Especially Atsuro's.
On Gin's path, you lose your demons, ALL of your demons, before going up against Babel's final form. This is annoying on your first playthrough, but your characters would probably be roughly on par with your demons so it wouldn't be THAT bad if you prepared for it. However, if you're not aware of how the fight works and are on your third or fourth playthrough, during which you probably completely relied on the end-game demons you carried over from each game, it's a good chance you'll lose due to being underleveled. Now, while the story hints at this, it's easy to assume you'd lose your demons AFTER Babel dies. Nope.
Super Robot Wars games have a bad habit of this; not only will bosses have absurdly high health, they'll frequently have scripted events where getting their health low enough just makes them restore it completely. The worst offenders are probably the Super Robot Wars Original Generation games. In Original Generation 2, any boss worth mentioning is going to have over 100,000 HP, and the last few stages will have lots of them in a row. All of the last three stages (four if you face the True Final Boss) are going to have over a million HP's worth of bosses, and that doesn't even include Mooks' HP.
The real offenders are the end bosses from Alpha Gaiden. Shu regens ALL his health 5 times.
Both Orcus and General Akhboob from Total Carnage. The game goes as far as to worn you that Orcus is "the mother of all boss monsters". Also, of the two, Akhboob is the only one with a health meter. And they're the only bosses of the game.
The final boss of Gundemonium Recollection, Elixirel, has 11 forms, one for each node on the Tree of the Sefirot. The good news is the 11th is the True Final Boss, so you only have to deal with 10 most of the time.
Dark Gaia, final boss of Sonic Unleashed will force the player through multiple rounds of at least three different, yet similarly difficult styles of gameplay that must be executed with near flawless percision to win. Mercifully, the game marks each genre change as a checkpoint of sorts, meaning that deaths aren't too frustrating.
Or you know This. Not only clocking in at seven minutes (while the average DDR song is under two,) it also has in the neighborhood of 2000 steps, meaning you can get multiple 300+ combos in a single song (where as 300 is about typical for one song on the highest DDR difficulty.) Granted, you have to find and download the song for yourself to run in Stepmania, but some of us go out of our way to run (nearly literal) marathons.
Special mention goes the Challenge courses in the US release of DDRMAX. In most games, this mode makes you do 4 songs in a row without stopping and little room for error. This game, on the other hand, makes you do 24 songs in a row without missing more than 3 steps total. On top of that, they're HARD songs.
The Big Bad Primagen in Turok 2: Seeds of Evil already has a ton of HP, and also has an annoying regeneration ability that can draw out the fight even longer.
Kingdom Hearts: Chain of Memories has Marluxia, the final boss. Most bosses have two, maybe three health bars. He has four. Not only that, but you can't actually damage him normally unless you go through his entire attack pattern. And when you do reach that point, you only have a few seconds since wind is blowing you off. Thankfully he's also open to attack every now and then, but it's unlikely you'll have strong enough cards to really exploit it until after you beat him.
Ansem, the final boss for the Reverse/Rebirth mode, is just as bad, if not worse.
Kingdom Hearts: Birth by SleepFinal Mix has No Heart. Like most Bonus Bosses in the series, he attacks almost constantly. On top of this he has 9 Health bars and excellent defense (Roughly 1800 HP and the most a player can ever do is 10-15 with maxed level and equipment). This amounts to 20-40 minutes of battling, monstrous compared to the 2-5 minutes typical of the series.
The series' other Bonus Bosses are just as bad. From Kingdom Hearts, we have the Ice Titan and Sephiroth. The Ice Titan is a pain because the primary way to damage it is to deflect one of its attacks back at it, which as the fight goes on, it will do less and less, and often whilst you are in no position to be able to deflect. Sephiroth is easier to damage, but has a ridiculously large shield to whittle down before his health bar even begins to deplete, and has attacks which will almost kill you, even at full health. Kingdom Hearts II has Sephiroth again, who has 15 health bars (the final boss has at most 7/8) and loves to do back-to-back Heartless Angels and Teleport Flashes before you can heal.
All Kingdom Hearts games seem to end with ridiculously long bosses. Kingdom Hearts II has a final boss with at least 6 different parts to it; one part, The Giant Nobody Dragon, is even split into 3/4 stages! Kingdom Hearts has a similar number of parts to its final fight. Kingdom Hearts: 358/2 Days has the fight against Xion, which contains 4 stages, and isn't even the final boss. Although, despite being the second-last boss, it's more of a final boss than the actual final boss, Riku, who doesn't have multiple phases.
During her first stageUrsula who can be this if you don't know the trick, which King Triton tells you. You have to use spells on her cauldron until it blows up in her face. If you don't do this, you'll have to hit her a lot because she's the only boss who doesn't take normal damage. Though, if you level up enough, Ursula can be easily defeated entirely without magic.
The boss of the Rubina level in Hydorah doesn't actually have much health, however there are two rotating rings of shields which make hitting it really difficult. Plus your weapons are almost certainly at the lowest level when you face it, given Continuing Is Painful and the difficulty of the preceding level. Expect to hear the music loop multiple times during the fight.
Unless you use the Wave, in which case you can defeat it in seconds. Unfortunately, you can't get the Wave until much later in the game, so it doesn't help unless you deliberately skip Rubina and come back to it later.
Tropicallo from Legend of Mana: instead of taking damage like a regular boss, it loses a set fraction every time one of its two tendrils dies. One of them is an insanely tough attacking type tendril, the other casts magic and has a humongous self-destruct attack when detached.
This gets turned Up to Eleven in the Nightmare and No Future modes - it does rather more damage, but is still a cakewalk. Unfortunately, while it winds up with a hundred health bars, the amount of damage dealt to it with each tendril's death doesn't increase, meaning that you will literally spend hours trying to put it out of its well-deserved misery. (Unless you turned off No Future mode before fighting it...)
Bosses in the Mortal Kombat series usually have much more HP or higher defense than normal characters, and most are SNK Bosses to boot.
Sa Ga Frontier 2: the final boss of the game, and the whole last dungeon. The final boss doesn't have a lot of HP (~60 000), but is empowered by his henchmen, the Anima Masters, which grants him special powers (such as healing or a OHKO move that can turn everyone to stone) and extra HP (which can double his initial HP) if you didn't defeat them earlier in the very last dungeon. The catch ? They are skippable, in a dungeon where you can't go back to fight them once they have been skipped (something a player can't possibly guess before reaching the final boss). Only 4 of them can be challenged to a fight, and two of them are Duel Boss, which lead to the loss of the character who stay behind, in what seems to be Heroic Sacrifice. On top of that, your party grows weaker and weaker after each fight, losing Mana Points which are difficult to resplenish if you don't have in your inventory the correct items (which are useless for 99% of the game : you may have tossed them because of inventory limits, and you can't use them during a battle!) which can lead them to be forced to use their own life force in order to continue on fighting. True, your characters do more damage the lower ManaPoints they have, but doing so will kill them once they run of Life Points (LPs). Now, take into account that unless you are Crazy-Prepared (which you will not be the first time), you won't do more than 2000 damages to the final boss per turn, and that this boss loves to depletes your characters of their LPs. Oh, and your main character only have 14 LPs, which means that unless you looted from one of the final boss's henchmen the one and only item of the game which prevents you from losing LPs when taking a hit, you'll hit a game over once she runs out of these (mind you, all others characters may die in battle, you won't get a game over). So, basically, you're stuck in a very long battle, where you must take down the final boss before it takes '''you''' down, and in which some party members may die permanently if they run out of LPs. Have fun!
Not nearly so bad as it's made out to be, as each of those can be bypassed: If the player moves extra characters to the reserve, you can take down all six of the Anima Masters...which has the unfortunate side effect of reducing your party for the last of them (admittedly, he's the hardest). There is also a guaranteed drop of a second item that prevents LP damage, much earlier in the game, but you have to choose to fight rather than bypass a particular battle. Admittedly the final boss is still lengthy in this case, making it as much of a Guide Dang It as a Marathon Boss.
This video. Even with the assistance of a macro to spam the fire button, it's still absurd.
The Bonus Boss of Tales of Symphonia who unlocks your Infinity Plus One Swords, Abyssion, is also a Marathon Boss, featuring higher HP than the Final Boss and a more dangerous base of attacks. The recommended strategy for dealing with him is to use an "All-Divide," an item which halves all assigned damage and thus makes it even more of a marathon. (The reason this is considered an improvement is that it does not change the effectiveness of your healing, essentially making those spells double-strength.)
Another Tales' Bonus Boss, Nebilim from Tales of the Abyss, is basically the same, except that there's no All-Divide. Fortunately her damage output has been adjusted downward for that reason.
Any of the "giant monster" bosses from Abyss's Unknown Mode, especially Replicantis. The very first monsterbattle on Unknown usually takes about 15 minutes, just to get an idea.
A rare Tales Series example in which the Marathon Boss is not a Bonus Boss: In Tales of Destiny 2, Fortuna, the Final Boss takes forever to beat. Look up videos of it on YouTube, and you'll notice that they're often split into multiple parts or have most of the fight edited out. The only indication that they're going down is that the music changes.
On higher difficulties, practically every single boss in Tales of Xillia ends up like this, due to how low the party's overall damage output is compared to other games in the series and the fact that bosses can escape from combos a lot more easily then in previous games. Only once one has fully powered up the Fell Arms and/or boosted their party's stats significantly with items do they go down in what could be considered a normal span of time.
Skies of Arcadia has a few, mostly ship battles like; Georgio, the Hydra and of course Zelos(hell all of the gigas count really). But it also has a tortoise boss battle where the boss can put up a shield to prevent you causing any damage and it will heal itself. It'll do this around every four turns so you better hope you can cause enough damage to keep up with it.
Bosses in The Legend of Dragoon are all like this due simply to the mechanics of the game. If you haven't played it, magic is outrageously rare and is pretty much for use on bosses only. Only two characters have healing magic at al (Shana/Miranda and Meru), but Shana and Miranda are so much better at it than Meru and Boss battles with Shana and Miranda take forever]], and the item limit is quite low. The way you heal is that every time you defend, you heal 10% of your maximum health. It definitely adds length to every boss fight. This isn't to say anything about the Final Boss, which requires you to take out as long as six hours unless the characters are really leveled up.
Bosses in the arcade version of Double Dragon II are in general much tougher than the first game, but Abore, the Andre The Giant ersatz in Mission 2 , takes the cake. It doesn't help that you fight two of him in the final stage.
Lord Burroughs from Clock Tower 3. First of all, he has two health bars while the other bosses only have one. Each health bar takes twice the damage of a normal boss. He has two main attacks; a tether ball projectile similar to yours, and a pool of red slime that traps the player for a few seconds, leaving them open to projectiles. He does have a sword, though he only uses it at close range. What makes this boss a pain in the ass is that when he tethers you with three balls, he does an instant-kill attack. These can be dodged by crouching, but using this strategy drags on the fight for more than half an hour.
ZOMG: The Landshark and Shallow Sea / Sea Lab X. It can take 6 hours to complete the latter with a full crew. On medium. The former takes around an hour to beat...with 20 other people attacking it.
Sealab X is peanuts compared to Kamila, the boss of Deadman's Shadow. While an entire Shallow Sea/Sealab run can take six hours on medium, just fighting Kamilia's Bloodlust form alone will usually take at least two hours, and that's if nobody wipes. Assuming everybody is Attuned, and everyone has their rings maxed to 12.0, an entire Bloodlust run can take as long as five hours, not counting time spent assigning buffs and time lost to disconnects and lag. If not everyone is Attuned, expect runs to last as long as eight hours or more, exclusive of buff assignments and time loss.
The Arishok in Dragon Age II has an extra long health bar, high defense, and also uses health potions. On top of that, his swings are very hard hitting, enough to knock you down each time unless you have high fortitude or are immune to knockdown. And he can get you into an infinite knockdown chain, meaning you're potentially done if he hits you even once. Have fun.
However, this is only if you duel him. He's way easier if you opt to face him along with his goons, because at least then you have a party helping you.
Magic: The Gathering's first video game, on the plane of Shandalar, featured the Big Bad Arzakon. On the easiest level, he has 100 life. On the hardest level, he has 400. To put this in context, in a standard game of Magic, players have 20 life, and in Shandalar, both you and the mooks tend to have lower life. But he uses a five-color deck with almost no mana fixing, so it's entirely possible that, even at 400 life, you're staring at just land on the other side of the table. Err, screen.
At least he's still vulnerable to milling and poison.
May God help you if you fight Borderlands' Final Boss on Playthough 2 Solo. If so, be prepared to spend about 15-20 minutes unloading all of your weapons into its weakpoint while being flung back by its shockwave and laser attacks. Oh, and if you die, its health fully regenerates. Ditto General Knoxx on Playthough 2.5. Not only can he easily kill in a single attack if you are not being careful, but he has Devastators in both Normal and Badass forms, as well as Lance Medics who can heal about 5 minutes worth of damage in 10 SECONDS.
The final bosses in most of the House of the Dead games, especially The Wheel of Fate and The World (two forms and two lifebars, to boot).
The Facebook game Viking Clan scoffs at those puny bosses. World bosses are meant to be fought by thousands of players together (anyone can take part in the battle). The Phoenix, the weakest of these bosses (Level 10, apparently), has 26,343,750,000 health points. That's 26 billions. The battle is timed, lasting 14 days, and individual players must wait 4 hours between attacks. Fortunately, it's really just a question of length as it doesn't seem to heal and deals very little damage.
The second boss in Fester's Quest, and most others.
Rinnosuke in Touhou Labyrinth. He has 7 different forms, can switch between the first 6 at will, and when he isn't using other forms, they actually regenerate HP. When added together, his collective HP more than triples that of the previous boss (Yukari) and her 3 forms.
The final boss battle in Child of Eden has about five forms and can take over 10 minutes to complete; witness it in all its glory here.
The final boss of Dawn of War 2: Chaos Rising has 3 million HP and can regenerate about 200 000 at a time. Your units can deal 1000-2000 damage at best. Kind of justified, since he's a Greater Daemon of Nurgle, and those are said to be able to destroy whole planets alone.
If you're feeling cheesy, a large part (or all, on easier difficulties) of his health can be drained by standing just on the edge of his boss arena and hitting him with a full duration Orbital Strike. If you don't come close enough to aggro him directly, he won't move an inch to dodge your giant death laser.
Also the Avatar in the base game, who requires thirty or forty minutes of beating on and running away to take down because he'll kill your entire force if you just sit around hitting him.
Tyr/Myria from Breath of Fire. Then again, you should have known after the previous bosses that after the health bar you actually see is only a fraction of their actual health.
The final fight against the Thugs 4 Less leader in Ratchet & Clank: Going Commando. Mostly because you'll be sat in a turret, constantly trying to shoot away his bombs, rather than actually just shooting him. Even the developers admit he simply has way too many hit points.
Many players will also cringe at the name Great Commander. Some may not, though, because they couldn't last through it and never learned its name. Six small hitboxes that are a nightmare to hit. And all of them need to be hit. Oh, and did we mention that this fight is a Spiritual Predecessor to the All Range Mode segments found in later games, so it's also a gimmick fight?
The final boss of the arcade game Dolphin Blue.Every time you think the fight is over, his machine just reconfigures itself.
Borderlands2 has BNK3R (pronounced "Bunker"), a giant, flying robot with a monumental amount of health. In addition, it likes to fly out of range of your guns, so for half of the fight it's almost impossible to deal any damage to it at all. Fortunately, there is a relatively quick (read: still slow, but not quite as slow) way to kill it - rocket launchers deal spectacular damage, with the downside that you can't carry much ammo for them at once, and the ammo is more expensive than normal ammo. This downside can be completely negated however, because there is an ammo-vending machine located near the area where Bunker is fought, and at that point in the game you have more money than God, meaning you can afford as many rockets as you need; but even then Bunker takes a long time to destroy.
There's also The Warrior, the game's final boss, which resembles a giant angry demon-dog with fire breath. This time, you can't run back and forth to a vending machine.
The third Sister Grimm in Shadows Of The Damned. There's actually a health vendor in the boss arena, which you will likely need if you don't know her weakness (fully charged skull blasts to the core).
The Brain Tank from Psychonauts. The only time you can even hurt it is for a brief moment when it occasionally tries to charge you. And you have to hit it quite a few times. Did I mention that it is throwing Interface Screw bombs at you the whole time? Or that this is merely phase 1, and you don't get to heal at all in the much more difficult phase 2?
The final boss of The Denpa Men. It's a Sequential Boss, so there's a lot of little fights in a row. While the first boss can be basically beat by barraging it with physical attacks, the second boss can use a guard shield to defend itself, and uses some more damaging attacks. But the third boss? In addition to having tons of HP and healing at the end of every turn, he gets two attacks every turn, he can easily sweep your entire party, he can use guard shields to completely neutralize damage, he flip-flops from being completely invulnerable to magic and being invulnerable to physical attacks (while still being fairly strong against magic), and, near the end of the fight, he flat-out becomes invincible for a few turns, and there's nothing to do but wait it out. Yikes. The whole sequence of fights can go on for nearly an hour if you're unlucky.
The final boss of the NES Licensed Game of Mad Max takes about 20 crossbow bolts to deplete one segment of his life meter. If you didn't collect enough ammo during the last Road War, you're toast.
In a rare Visual Novel example, the first Ace Attorney Investigations has the final confrontation against Quercus Alba. To put it bluntly, the entire first chapter doesn't even come close to the amount of time you'll spend watching every piece of evidence you have being shot down with reckless abandon by a single person. The fact that there's even a save point in the middle of it says it all.
There's a Match Three Game example, too. Normally when clearing the top of the screen, you're given a congratulatory message, but the first time you do so on level 166, you get the message, "The Lord of Shadowsis gathering his strength..." and are taken to another screen. It turns out to be a three-stage level, at the end of which one of his five heads explodes, meaning four more three-stage levels before he's defeated.
The Mini-Boss battles during the Bandit Spider challenges in Ōkami are this, since both the minibosses involved and the enemies have their HP significantly buffed. Among the regular bosses, there's Orochi and Yami as well.
The final battle sequence of Monster Girl Quest hits this big-time. Big boss battles usually take about 5 minutes; the final boss sequence has five stages and takes almost an hour. To elaborate:
Black Alice dies. Goddess Ilias promptly stands up out of Black Alice's melting corpse, revealing that she survived being assimilated, and that her subordinates' betrayals and her apparent defeat were all planned out in advance. You fight Ilias.
Big surprise!Ilias was also just playing around. Cue One-Winged Angel transformation and a 30-minute battle as the entire main cast co-operate to take her down.
Uses of this trope outside video games:
Problem Sleuth: The final boss fight with Demonhead Mobster Kingpin took up over half the comic, spawning an absurd number of fresh HP gauges at one point; being that the comic was a parody of Eastern RPGs, this was very likely an Affectionate Parody of the trope. Lampshaded by Problem Sleuth himself in his Strongly Worded Letter to the final boss.
In one of the Sword Art Online novels, Kirito told Lizbeth of the time he participated in a raid against a floor boss that was fairly weak, but had so many hit points that it took them two days to kill. They had to fight it in shifts so that every squad in the raid party could get some sleep.