Unlock Akuma as a Playable Character: At the 'Character Selection' screen highlight Ryu and press Down, Down, Up and highlight Ken and press Up, Up, Down. Then highlight Ryu again and press Up and highlight Ken again and press Down. When Akuma appears highlight Sean and press Down, Down, Up, Down, Up, Up, Up and press any attack button and Akuma will be unlocked as a playable character.
Fight Akuma: Get three perfect victories and Akuma will follow Gill.
Fight Super Turbo Akuma: Defeat Akuma with a 'Super Finish' in each round.
Fight Secret Opponent: Successfully execute 5 'Super Finishes' without losing any rounds.
Unlock Alternate Costumes: At the 'Character Selection' screen highlight a fighter and press MP + HP.