Answer
The answer is: Undefeated. Rocky Marciano, also known as the "Brockton Blockbuster," holds a unique distinction in boxing history as an undefeated professional boxer. Throughout his illustrious career, which spanned from 1947 to 1955, Marciano remained unconquered, winning all of his 49 professional fights, with an impressive 43 of those victories coming by way of knockout.