Fight as Akuma:
Select the "Game Speed" then choose the "Super X" character type on the 
character screen. Then highlight the following characters in order: Ryu for two 
seconds, T. Hawk for two seconds, Guile for two seconds, Cammy for two seconds, 
and Ryu again for two seconds. Immediately press Start followed by Three 
Punches (you can set then to one button, such as L1). Note: The time that the 
pointer highlights a character must be exactly two seconds.