Which moment/fight from your favorite fighter defined their career? His career-defining moment would be when he said 'no' to the Vietnam Draft and lost 3 years of his prime to stand up for what he believed to be right, and to stand up for black rights in America. Ali's fight, which is hard to pick since he has so many great options (Liston, any of the Frazier bouts, Spinks 2, etc) but I think the obvious answer is when he fought George Foreman, upsetting him to re-win the heavyweight championship. That would be his career-defining fight. Looking forward to these responses, should learn something new!