Pernell Whitaker IMO. I never saw him lose in his prime, yet alone early in his career, yet alone late in his career with the exception of Tito, and by then not only was it his age but he had also been heavy on drugs and had lost focus, was robbed in three big fights vs De La Hoya, Chavez, Ramirez. Only Ramirez would grant him a rematch with the other two being cowards. Not only would he beat his opponents but he would shut them out to where they wouldent even win a round, if he would have had any kind of power in his hands people would rate him as the greatest fighter of all time, either way I will still go with him.