Successfully complete the game with a flawless victory to everyone. If you did, you should have at least power 500. If you did not defeat everyone with a flawless victory, the ending will still be there if you have over 500 power, and no power codes.
Press Forward, Up, A with Buzz, Ty, or Kato to pick up your opponent. Press A again to throw your opponent down and do about 40 damage. Note: You cannot do this to the Masked Warrior or Eddie.