Dragon Ball Z: The World's Strongest (1990)

A scientist named Dr Kochin manages to free his master, Dr Uirou, with the help of the Dragon Balls. The resurrected evil scientist develops an army of great warriors and manages to hold Bulma, Piccolo and others hostage. Now Goku and his friends must figure out how to stop him before he takes over the world. This film takes place before the beginning of the Namek arc.