Thrill Kill Codes -

Fight as Cain, Judas, or Marukka:
Successfully complete the game under the medium difficulty level.

Alternate costumes:
Complete all of a character's moves in practice mode. Then, highlight a fighter and press L1 + L2 at the character selection screen.

BellaDonna's third "Thrill Kill":
Press Down + Square + Circle + L1.

Have Gimp in practice mode:
Complete practice mode with all eleven characters. Gimp will be unlocked at the practice mode character selection screen. Hold L1 + L2 + R1 + R2 and press X on any character at that screen to choose Gimp as your practice opponent.

Fight regular game in practice mode arena:
Complete practice mode with all eleven characters. Then, hold L1 + L2 and press X while any arena is highlighted.

Instant Kill Meter fill (beta version):
Press L1 + L2 + R1 + R2 + Punch 1 + Kick 1 + Select during a fight. Alternatively, hold L1 + L2 + R1 + R2 + Select + Start + Triangle + Square + Circle + X during a fight.