
Evander Holyfield (born 1962) is the only boxer to win the undisputed championship in both the cruiserweight and heavyweight divisions, and one of only three men to win the heavyweight title three times.
Holyfield's defining moment came when he stopped the previously unbeaten Mike Tyson in 1996 — a massive upset driven by Holyfield's exceptional heart and conditioning.
Reference:
TaskLoco™ — The Sticky Note GOAT