Edit: It wasn’t in the Ban Akuma thread that Sirlin mentioned this, but on his website:
http://www.sirlin.net/articles/street-fighter-hd-remix-akuma.html
This is a quote from the Akuma page:
Then I made one small change that made a world of difference. I allowed his air fireball to be performed very low to the ground. In the original game, it has a minimum jump distance before it can come out, but I removed this. Now it became possible to do a ?tiger knee? air fireball, meaning you roll the joystick from down to forward to up/forward (for a jump), then wait a moment for Akuma to barely leave the ground, then press punch to get an immediate air fireball. This turned out to be way more fun and versatile than I realized it would be.
Akuma can attempt many, many traps and setups with this. An example is immediate air fireball (I?ll call it TK air fireball, referencing the tiger knee motion), then land right next to the opponent with the cover of the air fireball. Then do, say, low strong, TK air fireball and land right next to them again. Then do low strong, low strong (pushes you farther away), and TK air fireball to reset the trap. This time, after you do a normal move or two, jump straight up and do an air fireball.
I just listed three different air fireball situations there: one TK from close, one TK from farther, and one where you jump straight up and don’t do the tiger knee technique. Many characters have to do a different move or act at a different time in order to deal with each of those situations. Against new players, I can create what looks like an inescapable lockdown, but really it?s a mixup that gives the opponent several chances to get out. It?s all an illusion.
I tested this trap against all 17 characters and every single one can get out. Ken can do a medium dragon punch (invulnerable on the way up) to ignore the entire situation. Zangief can use his green hand. Bison can just jump strong. Everyone can do something. Also remember that if these air fireballs hit, they deal only a couple pixels of damage. If they hit as Akuma lands, he can attempt to go into a damaging combo, but due to the way the game intentionally slows down when fireballs hit, this combo will fail about 50% of the time no matter how good you are.
The air fireball was a hit with playtesters because it?s so fun and feels so powerful, yet is actually beatable in many ways.