Goku and Vegeta form the iconic duo of the Dragon Ball franchise. Before becoming teammates fighting to protect the earth, the two used to be sworn enemies. The first battle between the two took place in the Saiyajin saga and it played an important role in the later development of the character.
In the Saiyan Saga, Vegeta is a villain who wants to destroy the earth, and Goku is the only one capable of confronting him. Although Goku is defeated, the Saiyan prince is also unable to move due to the injuries he received. In that situation, Krillin has the opportunity to eliminate Vegeta with Yajirobe’s sword, but spares his life at Goku’s request.
Later, in the Majin Buu Saga, Vegeta feels extremely resentful that Goku saved his life and became even stronger. So the new “brother” allows Babidi to try to control him with his magic to increase his strength. After gaining the desired power, Vegeta demands a rematch with Goku to try to prove his superiority.
Vegeta reveals that he purposely allowed himself to be blackened by Babidi, as he still remembers being “humiliated” by Goku having spared his life many years ago. From Vegeta’s point of view, he should have died as a proud warrior, instead of being saved by someone he considered inferior.
It turns out that Goku’s compassion fueled Vegeta’s hatred to become Majin Vegeta. Although he later admitted his mistake, Vegeta’s outrage is proof of the significant impact that the first fight between the two saiyan warriors had. With that, Dragon Ball strengthened Goku’s greatest rival, accompanying him to this day.