Dragon Ball Kai (2014) - episode 29 - 25 Oct, 2014

As Goku begins his battle against Buu, who demonstrates an ability to copy other people's techniques, Trunks arrives at Capsule Corporation, but struggles to find where the Dragon Radar is. Bulma soon realizes that she had left the Dragon Radar in her aeroplane, and manages to inform Trunks about it. Sensing Trunks has accomplished his mission, Goku undoes his Super Saiyan 3 transformation once more, and takes his leave after informing Buu that Trunks and Goten will be ready to fight him in two days. Shortly after Goku leaves, Buu, deciding he has no further use for Babidi, turns against him and kills him. (Source: Wikipedia)