-Nelson Mandela
edit: also, "If you want to make peace with your enemy, you have to work with your enemy. Then he becomes your partner."
Your statement on Mandela is un-nuanced and simplistic. We all evolve through life, hopefully for the better. Mandela clearly became one of the great 20th century champions of peace alongside MLK and Gandhi. None of them were perfect human beings, but that doesn't diminish their greatness at all.