Akuma

How do you get to fight Akuma in Street Fighter 4?

2 perfects and 2 ultra combos without losing. He'll challenge you after Seth.
But you'll have to have unlocked all characters except Akuma, Gouken and Seth.
At least that's how I got him.

Hmmm, according to GameFAQS you only need one perfect and no continues after having unlocked everybody, but Akuma, Gouken and Seth.

Akuma is one perfect, no continues, Gouken is 1 perfect, 2 Ultra combo finishes, and no continues, and Seth you get after beating arcade with everyone.

THis has been asked several times in the Street Fighter IV forum. Check it out.