Hardest bosses you've ever fought (spoilers)

[YoshiFlutterJump]

We all know that boss fights are supposed to be challenging. But some bosses...let's just say they go way overboard. Some of those bosses are just too difficult to be fair--and sometimes to the extent that they aren't any fun. That's what we'll focus on here. Just post the most frustrating boss fights you've ever lost (or perhaps won, after millions of losses).

My picks:
1. Miracle Matter (Kirby 64: The Crystal Shards)
2. Void Termina [Soul Melter EX] (Kirby Star Allies)
3. Cackletta [2nd fight] (Mario & Luigi: Superstar Saga)
4. King Dedede (Kirby Air Ride)
5. Petey Piranha [2nd fight] (Super Mario Sunshine)

 

[Minty]

Here’s one I would never fight, to be honest.

Nitros Oxide(CTR) from cheating at the beginning of the race, to having an infinite supply of items to take you down with, I'll tell you this: your 1000000th race against him will be your last!

 

[Teedgee]

-World 4 Boss (Super Bomberman R). The weak spots barely show up for a split second on top of them being hard to hit. I died a lot.
-MegaDragonBowser (Mario + Rabbids Kingdom Battle): It was only the first time I fought him, as I didn't have a good strategy, but he was such a pain in the butt. Now he's pretty medium to me.
-Yellow Devil (MegaMan 11): This is my first ever MegaMan game, so obviously the Yellow Devil is such a nightmare to take down. I somehow managed to beat him after several tries.
-ThunderBlight Gabon (Zelda botw): Like MegaDragonBowser, this one was only hard the first try. I managed to beat him without dying, and I literally jumped off my seat when I beat him. Might be luck tho.
-Giga Lakitu (Super Mario Galaxy 2): Now, beating this boss is cake, but back then, I was really struggling with this boss. I mean, I was like 7 years old at the time.
-Labyrinth Zone Boss (Sonic 1): This boss can be easy with practice, but it's not just hard, but really unfair, as you only get a shield before the fight and there's an obstacle course before the boss. Also, the boss itself is hard, and can hardly even be called a boss.

 

[Cocoa]

The Trash Can from Mario & Luigi: Bowser's Inside Story.

Yea, remember this little *bleep*?

This used to be the bane of my soul.

 

[Ray Trace]

In Garry's Mod, there's a fan-made addon called Vindictus Boss NPCs. Basically, this addon lets you kill these giant mofos from the eponymous MMORPG.

And more. There's a lot of them to play with.

Now, since it's Garry's Mod the ultimate sandbox you can easily cheese them with all the powerful tools in the game such as Ness's Homerun Bat, the Infinity Gauntlet or any sort of admin god weapon. You can give yourself god mode, yeah, or a lot of HP and shields. Since their AI is constrained within Source's limitations, you can also cheese by sniping them from far away.

But if you get close enough to them to be "aware" of you and you don't have any sort of cheats or cheap weapons on? It's hell. From their god-like amount of HP (in the range of 10,000 HP and more, the stronger NPCs that come with Garry's Mod like the Antlion Guard are only in the 100's.) to their powerful large AOE attacks, they take a lot to go down, and dish out lots of pain. And there's even a setting in the SNPC addon that lets you crank up the difficulty even more, and it's already pretty tough, even on normal. I typically use the Call of Duty World at War SWEPs to kill these but even then they're actually on the stronger end of the weapons than say, the default Half-Life 2 weapons you start out with.

In terms of other games with dedicated bosses, I haven't played Cuphead or Dark Souls but man, I'm not going to have the patience to beat those bosses after the hell the protagonists from those games are put through and what I've seen from them.

Of course, there's also the Super Smash Bros. bosses like Master Core but honestly, the hardest part about them is reaching the *bleep*er. Not that reaching it is hard. It's just that i have no patience to sit through the rest of the single player game just to challenge Master Core.

4. King Dedede (Kirby Air Ride)

That *bleep*ing timer is more of a dangerous threat than King Dedede himself. At the very least, in City Trial if the Vs King Dedede Event is the one active, that event spawns much more beneficial items than normal in the City Trial run and you're more likely to come across random All-Up patches here, which is very very neat.

Only two Copy Abilities are worth a damn here: Tornado and Spikes. The rest do jack in terms of damage to King Dedede, and you always deal the most pain when his terrible vehicle jams himself in a corner.

 

[Mcmadness]

y'all need to play more games.

 

[Ray Trace]

I definitely forgot about Metal Slug's bosses particularly due to how difficult the game itself is. Due to Metal Slug being in an arcade game, of course they're designed to be hard to extract quarters from you so it's a bit less...money hogging as it is in console versions of the game where you can just respawn if you die, even if you use up all of your lives midlevel.

I've played only Metal Slug X but that game is enough to list an honorable mention here in this thread. You will die multiple times just trying to destroy those large hulking things (due to the one hit and you're dead life system) and avoid their bullet-hell attacks. At least you'll get all sorts of cool weapons and mechs that often drops in those fights and those spectatular death animations from the bosses so it's satisfying as hell to land that finishing blow on those bosses.

 

[Mcmadness]

3 is even worse for attempting no continue runs due to it being the longest game in the series by far.

 

[London Parris]

The hardest bosses I faced is these, two of them are from Dark Souls:
Dark Sun Gwyndolin, Gwyn, Dreamy Bowser, Aesir, and Calamity Ganon.