If there's one thing I hate about MUGEN, it's Nightmare AIs. Custom AIs are good, as long as they're tough. But what I'm talking about is the AIs of fighters like Ogre, Elque, Evil Ken, and Evil Ryu. They are Nightmarish.
They don't give you a chance.
They exploit every possible weakness.
They use the same cheapo techniques over and over. And over. And over. And over.
Here's a testimony:
I had just downloaded the completed version of Evil Ken, whom I'd never seen before. I gave the readme a quick skim, and saw the part about 'kick[butt] AI!'
I smirked, thinking Reu was talking about the AI final bosses have. I've always loved a challenge. I fired up MUGEN, went into practice, and selected poor Mega Man to my character, and EK as the opponent.
You can guess what happened.
I was shocked. I had NEVER fought against such a powerful opponent (he drained Mega Man's energy in 7 seconds). I tried again, this time not touching the controls. Believe it or not, the battle lasted LONGER.
As for Reu's Evil Ryu, he does the same thing over and over and over... He gives me a slow Hadouken followed by a far Ashura warp. Depending on whether I'm crouching or not, he does a quick overhead/underhead attack (which makes the Hadouken hit me), followed by a trip, a Tatsumaki Senpu Kyaku, followed by a Shoryuken, followed with hyper, and then proceeds to beat the snot out of me.
Bottom line: AIs are supposed to be fun. Nightmare AIs aren't fun, they're torture.