Hardest game/difficulty in a game you've ever beaten?

I think mostly it has been CoD games and Halo's. CoD the grenades feel a little overboard and Halo's the bullet soak seems a bit over the top. 
 
Older generations, but not too older, Ikargua left my butt sore on the hardest difficulty.

" Whats with all these modern games? You guys are pussies. The Lion King for SNES was a motherfucker (some of you know what I'm talkin about.) "

I suppose that would be unlocking and beating every cup on F-Zero GX on every difficulty.

" @ZombieHunter said:

" @BionicMonster said:

" Whats with all these modern games? You guys are pussies. The Lion King for SNES was a motherfucker (some of you know what I'm talkin about.) "

Damn straight  "

Demon's Souls walks up to you, knocks you over the head with a mace, bends you over a table, and (BLEEP BLEEEEEP BLEEP BLIPPITY BLIPPPPPP BLEEEP)
@Stealthmaster86: I shat bricks when I finished MHC on Veteran.
@benjaebe: Fucking ghosts and goblins, NOW this thread is over. "

Streets Of Rage 3 on normal and Devil May Cry 3 on easy (the first, original, hard-as-shit version).

" I Wanna be the Guy on the hardest difficulty.   Nah, kidding. I can't even pass the third screen :P Mine's probably Arkham Asylum on the highest difficulty. It's not an excessively hard game, but it has its tough moments. "

F-Zero GX.  It took me weeks of devoted playing to become good enough to unlock all of the cars, custom parts, and arcade cup tracks.  Memorizing every split-second turn and staying alive down each no-rail stretch of track took immense concentration.  It was so easy to make a tiny bad maneuver and get sideswiped by the enemy cars and sent flaming off the course, 1st place out of reach for good.  I still never managed to complete the single player "story mode" on anything more than normal difficulty.  That story mode was insane.  
 
This is one game I'd love to have an online multiplayer version of.

I play singleplayer games for fun. If I want a challenge I play multiplayer games.

I have beaten Halo 3 Legendary, CoD4 and MW2 both on Veteran. I really didn't have much trouble with any of them. Halo 3 was the easiest out of all 3 by far, CoD4 the hardest if you discount MW2 SpecOps and include MHC.
 
Nothing has even come close to the difficulty I'm currently having with Bayonetta on Normal. Mind you, I haven't played any of the DMC games beyond the first couple of hours.

Ninja Gaiden Black probably.