Sometimes you run into games by developers who are generally sane, but make the ending of their game a horrible experience full of annoyance and "wtf?". It's like the idea of parting with the player terrifies them and the want to design the end as painful as possible, to force the players to turn back and hunt for collectibles or something. Any examples you can think of? Final bosses? Sudden gimmicks?

Here's Level-5's Rogue Galaxy on the PS2 for example. 10-stage final boss. The first two stages are easy, because you can use your normal party, complete with mutual healing and revives. Then they split up: each of the eight main characters, including the ones you never used, has to fight a real boss's body part.
Two of the fights are identical and have you fight a sub-boss, that (if you get the pattern) will never hit you over the course of those several minutes it takes to wear down the long health bar. Two other fights are identical too and are slightly more dangerous, in the sense that the sub-bosses can actually move. Then there's a stupidly easy one, where your character will most likely be able to "shoot the core" to death before its guardian can even scratch you. The next boss can be stunlocked to a quick death. The penultimate boss hits for about 9 damage if you block, while the character facing it most likely has at least 800 HP.
Then the really-really final boss comes, and it turns out that not only does it have attacks hitting a third of your health bar, but it can chain a few of them so quickly, you won't have a chance to heal. Naturally it also has an exploitable pattern, however you won't know it the first time you get there.
Now here's the best part: no continues between the stages. No try again. No revives, since everyone is solo and no one else is there to throw a potion. Almost every boss in the final 8-chain can hit for 1/4 or 1/3 of total HP if you don't know the patterns, and if you do, is wastes your time by having way too much health. Aargh!

I have two.

McPixel's final stage makes absolutely no sense at all. AT ALL. You have to pick six different triggers in a specific room, only you get no clues as to which are the correct ones. So you have to play through all six stages over and over again until you smack the right trigger. I spent twenty minutes running around until it finally said "OKAY YOU'RE DONE" and then the ending happened and I wanted my money back.

The second is Sly Cooper 1 on the PS2. The end boss is a flying stage, after you beat him up then you have to go through a platforming section where the platforms are really tiny. And if you don't make it to the end, you have to start the boss fight over from the start. That's eight minutes of fighting, every time. I actually gave up on that game at that point.

I would recommend Son Son II for the PC-Engine.
Its a platform game. Very good playing and graphics.
Only if you reach the end its insane.
You must beat every boss again....without healing between.
Oh, and there is no save option (usually you get your code in
other games).

I think any game that has a multi-boss final boss is close to having an awful endgame. Castlevania 64 definitely fits the bill. I spent a long time playing this game. The Nintendo 64 was at my grandparents' house, so I could only play the game when I was there. It took forever to get to the end (especially since I first played it on Easy, and then discovered you can only play half the game on that difficulty; to finish it, you have to play it on Normal... from the beginning), and when I got there, I was stuck. You first fight one Dracula, then you have to quickly leave the building because it is falling apart. Then you fight the real Dracula, who can teleport about the room. If you manage to beat him, you then have to fight this weird dragon-lizard-thing (and as far as I know, there is no explanation for where this thing comes from). I never could beat that last thing. It had some crazy attacks, and despite looking up a strategy for it, the strategy didn't work. I never beat Castlevania 64, and that makes me kind of sad.

Ciffhangers.

To be resolved in the sequel that we'll make soon if, uh, what ? Oh.

I vote Freelancer. The final part of the game is unforgiving at the best of times.

Some fighting games have totally unfair final bosses. Akuma, Gill and most KoF bosses immediately come to mind.

Oh, the old 8bit ones that gave You a "GAME OVER" screen once they were finished.

Agreed. It kind of comes up from nowhere as well: one moment you're fairly free to fly around and do whatever you want (gathering money for upgrades, mostly), then you are suddenly sucked into a sequence of missions that you can't break out of. It would be nice to be able to repair the damn ship every once in a while, too. Not that it matters, because of course mine had two missile launchers... and you can't restock on missiles in between missions. Fire the last one and you're fucked, because that leaves a battery of cannons that isn't worth jack.

I'm going to vote every game that isn't a shooter but forces its shooting mechanisms down your throat at the end because that's the only kind of epic and satisfactory ending that the developer could think of. Alpha Protocol is a prime example, and I've heard that L.A. Noire possibly even worse.

I was going to say Fallout: New Vegas as well, but I will probably forgive the piece of shit for once - it wasn't designed to be buggy.

Off the top of my head, the last stages of Drakan Ancients' Gates on the PS2 were terrible - this nice adventure/action/rpg game turns into horror trash AND sends packs after packs of monsters at you. I don't think I'd ever be able to beat it but thankfully god mode could be turned on.

Any game which utilises the "Japanese-style brutal final boss" gets my vote. This is the kind of boss which is either (1) multistaged without breaks, as mentioned above, (2) requires you to have upgraded your player/party in a certain way, or possess a certain object/skill, without the game making that clear, in order to pass, or (3) uses moves, techniques, or abilities which you have not encountered anywhere else in the game and which it is not made clear how you counter those. Bosses which employ these and also have instant kill attacks, summon annoying henchmen, or require you to sit through a long cutscene, move to the front of the "terrible" queue.

Funny enough, I really enjoyed Shadow Of The Colossus, which is a game of nothing but boss battles. But those felt fair.

Well the beat-every-boss-again endgame is always fun (Mega Man), but one of my personal favorites is the you-didn't-really-beat-the-game-yet-congratulations ending of games such as Ghosts 'n Goblins where you have to complete the game twice before you get the real ending.
And if I remember correctly to get the 'good' ending (those hidden 'good' and 'bad' endings were also great) in the sequel you had to complete the entire second playthrough without dying more than once per level or something.

A little different I think from the posts above, but I find 4X space strategy games tend to get less interesting in the end-game - and not just because you are simply rolling through what is left of your opponents. Technology simply reaches a point where it becomes so overwhelming that there is little real strategy necessary anymore. I tend to prefer playing the beginning and middle stages of development more. Often I find myself wishing I could almost "pause time" and play a game during a particular technological era and just play in that era - maybe with some tech advancement, but not all the way.

While I like to have technological progression, I think 4X space designers go far to into "uber-super weapons/drives/etc..." that I wish they would shy away from or still provide some sort of drawbacks to allow some thought about their use. So I think end-game design tends not to be very good, perhaps not totally awful, but not good in a lot of 4X space strategy games. It's something that has always irked me.

Interesting topic. I'm kinda surprised no-one has said the original Ninja Gaiden for the NES. The final boss has three stages, IIRC. If you fail in any of the stages, you. Go. Back.

For me personally, Baldur's Gate II's expansion Throne of Bhaal takes the cake. You fight against an evil wizard Melissan, although you wouldn't immediately believe she's evil because she masqueraded as a good person before, and before her transformation she looks kinda cute and frail. In the end, the end boss and her powers are just something pulled right out of the developers' asses. She's even more powerful than the main villain in the series, Irenicus, who actually got some character development, unlike Melissan. Anyway, I digress. Her boss battle includes four stages, and while you can save your game between those stages, you cannot rest. Which means, unless you were smart enough to include the Wish spell (high WIS characters get the choice of wishing for a good night's rest) on your wizard's spell repertoir, provided that you have one in the first place, you will have to beat all stages without a chance to heal and re-memorize spells in between. And let me tell you: Good fucking luck trying to do that. In true D&D fashion, she has lots of resistances, immunities and agility. She likes to summon monsters a lot. You probably would have either a) used all resistance breakers by stage 3 or b) pulled all your hair out.

All in all, she's a major pain in the butt.

Has nobody said "Xen"? I know everyone else is talking about raw difficulty but your opening paragraph left the window open so I'm still going to say "Xen." Not only is it thematically jarring ("Escape the undercomplex while under attack from nearly everyone and under the influence of the mysterious G-Man!" becomes "Space Marine! You're a Space Marine!") but the late-game introduction of long-jumping, sudden over-relance on jump pads (that didn't work on Earth or otherwise) and non-puzzle bosses just made the whole thing a mess. It's not malicious design so much as naive - you've never had to jump from flying stingray to flying stingray and surprise! It doesn't work!

Sure, it makes sense that the alien landscape of Xen should be weird, but that doesn't mean it makes for good gameplay. I dread going to Xen, and didn't really feel that upset when Black Mesa was released without. Sometimes you have to remember that just because something works within the universe doesn't mean it works when the work is consumed in the real world. Your story may involve your character falling in love with an adorable puppy, but if you think it's a good idea to spend a mission escorting it through a minefield, you might want to consider writing around that scenario instead of forcing the player to experience it.

Ironically it was Blue Shift, which did very little right, that actually did Xen right. Not only did Gearbox realize not to include any jumping puzzles, but it follows along the same lines as the rest of the game. The armour system in Blue Shift does an interesting thing to your play style, in that forces you to move on once you have your armour instead of having a safe place to return to like the chargers Gordon and Adrian Shepherd got. But it goes beyond the armour system: you spend all of Blue Shift looking for resources and never having enough of them. Not just armour. You go looking for people, batteries, that sort of thing. When you get to Xen, and you find the resource you're looking for, the game suddenly drops late-game enemies on your head in a stream. This could have been cheap (and if you've played Decay, you know it is cheap) but when I play I get this rush of panic reminding me that I'm not Gordon Freeman and don't have the weapons or armour to fight this, and run away. And that feels like the point. You're the weakest of the three/five HL1 protagonists, and the expansion pack has spent its full duration trying to teach you that, and you're in enemy territory. Get the crap out of there!