Me playing as Kasumi naked in Dead or Alive 2: Hardcore for PS2, I used an Action Replay MAX to play as her. Hard to believe this is a hidden.
This isn't technically a hack - it's a custom Action Replay Max save file that uncovers an existing (but hidden) element of the game. When Tecmo made Dead or Alive 2: Hardcore for the PS2, they included a nude Kasumi polygon model, but dummied it out during normal gameplay.
Special Gameplay footage from Dead or Alive 2 for the SEGA Dreamcast. Kasumi is fighting against naked Kasumi? VISIT: Master K.