

After Vegeta witnessed Goku’s display of power, he vowed to never allow Goku to be stronger than him again–leading to a productive rivalry that has led to both fighters attaining vastly powerful transformations. During the Frieza Saga, Goku surpassed the previously superior Vegeta by attaining the transformation of Super Saiyan. After that pivotal moment in Vegeta’s life, he slowly started aligning himself with the Z-Fighters more and more, all while telling himself he was doing so to keep an eye on Goku.

Vegeta didn’t become an ally of the Z-Fighters until he joined them to fight against Frieza on Planet Namek. However, the other Z-Fighters used their combined efforts and beat Vegeta, nearly killing him in the process.

When Goku tried to stop him, Vegeta actually proved his superiority and defeated Goku in a one-on-one fight. Goku and Vegeta began their relationship as bitter enemies as Vegeta was a villain who invaded Earth with the intention of wiping out all life on the planet and then selling the vacant world to the highest bidder.
