DRAGON BALL: THE BREAKERS

You can unlock this by simplying achieving raider Level 4. This is achieved by finishing off survivors and civilians. It takes roughly 10-15 kills to achieve this (remembering there is 7 survivors, if a survivor is revived after finishing them off, they can be finished off again and that civillians count towards this number).

In the case of Majin Buu, you will achieve level 4 after Innocent Majin Buu has been rescued - I believe this is easiest to achieve with Majin Buu of all the raiders.

I created this video to help:


Hope this helps.