Fight Hannya
To fight against Hannya (Evil Bishamon), chose the punch color if you are on the 1st side or the kick color if you are on the second side. Then end the game without losing a single round. You also need to get 3 ex super or Darkforce finishes. if done correctly, Hannya should challenge you after your last boss.
Play as Jon Talbain from NightWarriors
To play as the Night Warriors version of Jon Talbain, press and hold START, move to him then press all three punches or kicks.
Shadow Mode
At the fighter-select screen, put your cursor over the random "?" box at the bottom. Press Start five times, holding the button on the fifth press. While holding start, simultaneously press all three punch buttons. You will become your last opponent when you defeat him/her.
Fight Hannya...