The last fighter to go for 49-0 was Larry Holmes. He was 48-0 when he went against Michael Spinks - 09/21/1985. Spinks won in the 1985 "Upset Of The Year" according to Ring Magazine.

Just as Mayweather has done, Holmes "bad-mouthed" the only fighter to retire @ 49-0 - Rocky Marciano.

Here is my autographed Marciano menu. He retired from fighting at the age of 31. Unfortunately, he died in a plane crash on August 31, 1969 - the day before his 46th birthday. Not a lot of autographs out there.