The Marciano-Walcott shot is one of the greatest pics in boxing history. It was the 13th round of their first championship fight. Marciano was clearly losing — and he won with a knockout with this single punch.
Walcott later said that he never saw the punch coming. The two had headbutted early in the fight. Just before this punch, Walcott had pulled back from a Marciano punch, and some blood had dripped into his left eye. So, when Rocky threw the right hook, Jersey Joe did nothing to pull away from the full impact.
Jersey Joe later said, “Had I seen it coming, I would have pulled back. Rocky threw the punch so hard, he likely would have spun himself around and fallen to the canvas, too tired to get back up.
By the way, Jersey Joe lost the rematch to Rocky in the second round of the fight.
I'm not sure that this picture is of "the punch." It appears that both men are essentially parallel to the ropes - in the knockout sequence Walcott had his back to the ropes and Marciano had his back to the center of the ring. Marciano landed several big right hands late in the fight, so this could be one of those. Anyway, it is an impressive punch.
The final punch is probably the greatest single punch ever thrown. While you might be able to point to devastating knockout punches just as impressive, none will match Marciano's in terms of historical importance. It launched the Rocky Marciano era and salvaged a victory from what was probably the closest Marciano ever came to losing a fight. It allows Marciano to begin his reign and end his career as the only universally-recognized undefeated world champion.
Yeah, that was some punch. They don’t make men like Joe and Rocky anymore. Rocky got out at the right time. Today fighters never leave the sport, and you can see the damage that was done to their heads.