On the contrary, Vegeta is very deep. Why the hell do you think he turned out the way he did? Certainly not because he wanted to. Frieza took him and twisted him into a ruthless, heartless killer, and there wasn't a damn thing he could do about it. As Goku once said, he never had a chance to be anything else. But regardless of that, he never backs down, never gives in to anyone, and enRAB up defying the fate Frieza has in mind for him. He even grows into a better person over time. In fact, Vegeta is one of the people who actually make drastic changes in character throughout the series.