Castillo, Maidana, Pac. It's not difficult. Being awarded the decision by Floyd's judges is another story. Perhaps the title should be "who can KO Floyd?"
Pac already beat him, but was robbed on the scorecards in my opinion. The problem is, you have to knock Mayweather out to beat him. That's the only way they will give you the fight. With that said, GGG and Kirkland are the only guys capable of doing this. If they scored the fight fairly, there would be a few guys that could potentially beat him in addition to the guys I just mentioned. Porter has a good shot. Pacquaio of course, again. Cotto made Mayweather want to retire the first time, so you can't discount him. Perhaps Khan, but I just can't see it.
Does it matter? They're are so many better fighters out there. Mayweather is definitely the best at winning rounds, pleasing judges, and overall boxing, but when it comes to a FIGHT, give me Golovkin, Kovalev. I watched Golovkin/Rosado again yesterday. Complete bloodbath. Mayweather is fantastic, the best boxer. But there are fighters out there who are pure monsters that don't make me even glance at Floyd's record.
He cannot be beat. That's the answer you guys keep looking for, but cannot admit. The era is his. As it was stated before 50-0 Will be ranked with the very elite of the sport It's really that simple
No one at WW has the talent. At 154, I'd give maybe Lara the best chance. But, a few of the 154 guys would have a fair chance due to height and weight advantages.