Vegeta has the best villain arc of any character.
It happens soo naturally over multiple seasons I cant think of another character with such an intricate and well fleshed out arc as vegeta.
it certainly didnt take the easy way. which is when the murderous psychopathic murderer see "da killing is bad" and somehow changes.
Vegeta's starting point isnt even as simple as a "murdering psychopath". once you realize his back story and what happened with freiza its far more complex than that. he doesnt just become good either.
when on Planet Namek he's reluctantly kinda working with Gohan and Krillin but only to get the power to beat Freiza and basically replace him. He still murders Namekians and would clearly kill Gohan with no thought.
it isnt until arguably when he sacrificed himself against Buu, where he becomes "good"