Conversation so far:
what happened to Joe Frazier in the summer olympics?
In 1964 heavyweight representative Buster Mathis qualified but was injured so Joe Frazier was sent as a replacement.
how was Buster Mathis injured?
He injured his hand.
Are there any other interesting aspects about Joe Frazier?
Once, Joe Frazier battled Jerry Quarry in Madison Square Garden.
did Joe Frazier win his fight against Jerry Quarry?
Joe Frazier won the fight in the fifth round with a strong left hook to the ribs.
what did Joe Frazier go on to do after his victory over Jerry Quarry?
In March 1975, Joe Frazier fought a rematch with Jimmy Ellis in Melbourne, Australia, knocking him out in nine rounds.

Question: what was his greatest win?
Self-contained rewrite: what was Joe Frazier's greatest win?