There were those:
Spoiler, click to toggle visibilty
Play as Dio: At the character selection screen, hold B and press up, up, down, down, left, left, right, right, BC.
Play as Son Guko: At the character selection screen, hold C and press up, up, down, down, left, left, right, right, B + C.
Fight as Zeus In a 2 player VS mode battle, at the character select screen, hold B and C, and press A.
But don't remember if I ever tried them out. Probably the best way would be searching with artmoney for health value. Search for unknown value, then sort values that lowered when received hit and raised when new round starts and repeat until you find it it won't take veeeery long, but yeah, a bit tedious. Repeat same process for enemy and kill them with one hit setting low their health until you get where you need to, then freeze own and opponent's health(and time of course) and start ripping.
You probably won't find already made cheats useful for you...
