For Vegeta, there are probably 4 moments. One, when he's giving his last dying words to Goku to beat Freeza, with tears in his eyes. Two, when he attacks Cell mercilessly after Cell kills Trunks. Three, Vegeta making the ultimate sacrifice to defeat Boo. Four, Vegeta finally admitting that Goku was number one. Previously, I had been irritated by Vegeta's constant "I want to beat Kakarot" attitude. But those four defining moments made me accept him for who he is.
Mr. Satan. One, throwing Android 16's head over to where Gohan was. Two, helping Fat Boo become good and forming a friendship with him. Three, being the reason that Goku could get enough energy for the Genki-Dama. I liked how he actually became friends with the Z-Fighters and lost some of his arrogance, when previously, he fooled himself into thinking they were using tricks.
Broly. I don't really dislike him, it's just annoying how I see some DBZ fans go on about how Broly is so strong and that he's as strong as a SSJ3.

But him screaming "Kakarot" like a bloody moron is infuriating. I only liked him...when he was dead.