In The Buu Saga Vegeta let's Babidi take control of him, and wants to finish what he started with Goku because in Saiyan Saga they met the first time and they fought the first Time and Goku bested him, See that's why Vegeta wants to finish the fight with Goku and then Majin Buu set free and so Vegeta knocks Goku unconscious and goes off to face Majin Buu by himself, and he also makes a Sacrifice to destroy Buu Completely and that was it for Vegeta.
