Dragon Ball Kai • S07E58 : Emergency Escape from the Body! Buu's Retrogression Into Evil!
As Vegeta recovers, Goku continues to fight the thought form of Super Buu. Goku is rapidly losing energy, and just as Super Buu is about to defeat Goku, Vegeta cuts down the pod containing the fat Majin Buu. This causes Super Buu to go mad, as without the fat Majin Buu absorbed, Super Buu cannot exist.