Dragonball Z: Budokai
Adept World Tournament:
Beat Novice, then buy Adept World Tournament from the skill shop. It will appear in the recommendation category.
Advance World Tournament Mode:
Beat World Tournament in Adept, and then you can buy Advance World Tournament Mode in the skill shop. It will appear in the recommendation category.
Beat World Tournament in Adept.
Unlock Great Saiyaman:
Beat World Tournament in Advanced mode.
Unlock Everyone except Hercule and Great Saiyaman:
Play through the Story mode and defeat everyone. This will unlock new characters. Now play through again and defeat everyone including the new characters to unlock the remaining characters.
Thanks to Revolution reader zboy!