There's not a lot Mayweather has not done...undefeated in all 40 career bouts with 25 knockouts. Mosley not too shabby either, 46 and 5 with 39 knockouts.This follows Gus Johnson's comment on a recent Showtime broadcast that Mayweather was better than Pacquiao because he was undefeated and Pacquiao had lost three times. Of course, you don't measure boxing greatness by the zero in the loss column, unless you are Floyd Mayweather or you don't know much about the sport. Consider: Muhammad Ali (five losses) is considered far and away a better fighter than Rocky Marciano (zero). Duran's on most people's top-ten all-time list despite having lost 16 times, including one of the most famous tank jobs in the history of sports. Sugar Ray Robinson is generally considered the best fighter in the history of the sport, despite losing 19 times.
The smarter observers measure boxers by whom they beat, and, the anchor's comment notwithstanding, there is in fact a lot Mayweather hasn't done. Notably, he hasn't ever beaten a welterweight widely thought of as elite, despite fighting at 147 since 2005. For that matter, the closest he got to an elite fighter at 140 was Arturo Gatti.