Floyd Mayweather Jr.

Floyd Mayweather Jr. retired with a perfect 50-0 record, including 27 knockouts, making him the only boxer to retire undefeated as a champion across five different weight divisions. His defensive style made him extraordinarily difficult to hit cleanly throughout his prime. His 2015 pay-per-view fight against Manny Pacquiao drew roughly 4.6 million buys, a record at the time that reflected the sheer scale of anticipation for the bout.