MK2 especially Mileena.
Fatal Fury Special, hands down. Super Turbo seems reasonable compared to it.
Sais every time you jump?
X-Men Children Of The Atom is full of shit. And not just the last boss…every CPU controlled character is absurd.
Actually every fighting game made before 1996 has ridiculously cheap AI, and that was intentional. FGs were so popular back then that the developers simply programmed the AI to rip off your money as much as possible until some other player challenged you or you quit in disgust (only to be back the next day to try again like an idiot).
As the popularity started to decrease they started making the games more fair to atract casual players, but it was too late.
Samurai showdown and metal slug comes to mind.
KOF94. The AI takes the human element completely out of the game. You can’t mix it up against it because it always has the right option in response to what you do.
Maybe I was just shit at them, But Grok and Exor from the n64 game ‘War Gods’ was complete bullshit.
With Grok it was LOL BELLY FLOP BELLY FLOP BELLY FLOP LOL STOMACH SLAP HOWD YOU LIKE THAT SHIT IN YOUR FACE
and with Exor, damn.Cant even remember the games I had with him.I know I only got up to him a couple times though.
Im definately shit at Third Strike and RESSSUUURRREECCTTIOOON never Fails to piss me off.
XBL Uno is fucking cheating fuck shit.Fuck that yo.
Nobody believes me when I tell them either. 
Oh shit I thought I just sucked at ST before I read this thread.
Samurai shodown and I agree with children of the atom.
Off topic: anything that wants to kill you in ninja gaiden
Guile in WW/CE/HF with those instant Flash Kicks. That always made me WTF. For some reason in SVC Chaos he’s semi boss like. Which pretty much equates to if you jump then you die.
Slash Man from Mega Man 7. That nigga be cheating all the time. He just seems to be in the right place for the pillage and rape all day.
I gotta chime in about UMK3. It just seems that whoever is 4th is gonna rape you. But that has more to do with the game sucking quarters than just AI alone. But Jade or Cyrax is usually in that spot. A fucking conspiracy, yes.
Gill aint shit. Resurrection is just scary as fuck though. It’s tough to see your hard work go to shit because you mistimed the move to stop him get his life back. I think while NG and 2I have easier Gill’s I love 3S because every now and again Gill will be nice in a deciding round and use Meteor Strike/Seraphic Wing and you proceed to stop that and beat that ass. That fight is more about managing Gill’s meter and let that be the factor on how you go on offense.
SNK bosses. Fuck Magaki, Omega Rugal, Hell Gaoh, Ryo Sakazaki (FFS), White, Geese Howard (AoF2) and Team Boss (Reg A). The only issue with SNK bosses are that they usually have access to some nasty move or attribute that makes them. But in that there’s usually some fatal flaw in there for the player to exploit most of the time. Finding that is the key to victory. Other times the game reads inputs or you die as soon as you make a mistake.
I used to big up Sissy from PIM but you can chesse Princess Loli to death easy with most characters. The key to beating her is to know she reacts the same way every time to the same instance. Use that to exploit her.
Brawl on Intense is ugly especially in the Subspace Emissary when you have to play on it to get trophy drops more frequently.
I used K-Blanka(4) myself.
idk which game it was, but i remember starting a game with a asian punk character with a beanie on, it was a stage and a little pope girl. I was pissed to begin with; my wallet ran out my house without telling me where it went. I start the round up by backing up…and this little bitch has a box full of strong men, magic and some repitive movements. After 1 hour of being on the verge of crying, I quit the game. I dont know who made that game, but he needs to get jumped
That’s Sissy from Power Instinct Matrimelee. Look at my post above for the secret for taking her down.
Matrimelee.
World Heroes 2’s last boss is pretty ridiculous, if you’re just going by last bosses.
Def. Unlimited Hazama from BB:CS he was a bitch to defeat
Mizuchi from NGBC!!
I fucking hate him to holy hell!!!
nancy tekken 6
Holy God Earth from Spectral vs Generation… maybe I just don’t know the game well enough, or haven’t found the proper exploit, but for the life of me (or my character’s life for that matter) I can’t get around his cheap tactics. I mean he landed a 36hit super on me, after a knock down, while I was still flat on my back!!! Talk about fighting dirty.