Kick Them When They're Down
Press Start when you win a round. You can now walk around and beat up the character on the ground.
Play as Akuma
In the character select screen, go to Spiral in the lower-right corner and wait for two seconds. Then move back to the left until you reach Iceman. Next, move one space to the right, one up, two right, and one down. You should arrive on Silver Samurai. Wait two seconds and then press Fierce Punch+Light Kick+Fierce Kick.