"Piccolo is one of the few that started as a villain"

(Pretend I'm saying this like Rapper Boy)

Chazou

Tien

Vegeta

Android 18

Android 16

Android 17

Granola

Broly

Yamcha

Puar

Oolong

Gamma 1

Gamma 2

Dr. Hedo

Hit

Beerus

Majin Buu

Majin Duu

Majin Kuu

(Don't take this as offense I just wanted to state that there are a lot of other characters that have turned good after being bad, continue writing)