The easiest way to do this is to select SS Goku, Bardock and Majin Vegita as a team. Begin with Goku and keep blasting him. Whenever your energy level starts to go down too far switch to Bardock and keep blasting. Eventually he will get around by which time you will already have him down far. When your life gets into the red use Goku's ultimate attack and if Goku dies try the same technique with Majin Vegita. If you do not get it, try again.
To unlock Majin Vegeta ( Evil vegeta) You must complete mania difficulty of maximum mode, you will unlock him that way. You can also use Majin Vegeta ( Evil vegeta) by selecting vegeta and babidi as your team selection, you will be Majin Vegeta ( Evil vegeta) Through Babidi's Magic.