Rocky Marciano was a professional boxer who competed in the 1950s and is best known for his undefeated record of 49-0, which includes 43 knockouts. 


He was the Heavyweight Champion of the World from 1952 to 1956.


Marciano's record is considered legitimate by many. 


He fought and defeated many top contenders of his era, including Jersey Joe Walcott, Ezzard Charles, and Archie Moore. 


He also had a reputation for being a hard worker and a determined fighter, and his knockout ratio is one of the highest in heavyweight history.


However, some critics argue that Marciano's record is somewhat inflated due to the lack of top-level competition he faced during his career. 


His era was not considered the strongest in heavyweight history, and many of his opponents were past their prime or not considered elite fighters. 


Additionally, Marciano retired relatively early at the age of 31, and some argue that if he had continued fighting, he might have eventually lost a fight.


It's worth noting that in any sport, the perception of an athlete is subjective and can change over time. 


Marciano's record stands as one of the greatest achievements in the sport of boxing and his legacy lives on as one of the most iconic figures in the sport's history.