Armstrong, Leonard. Def Armstrong. What boxer you know has ever held a featherweight, lightweight and welterweight title at the same time. Today, that's 5 weightclasses, 21lbs.
Henry Armstrong for me. others considered: Ali, Ray Leonard, Benny Leonard, Sam Langford, Roberto Duran, Joe Louis, Willie Pep, Harry Greb
first off dude... you were fine with just best.. not bestest... just so you can know for the future man.... Me personally... i think Sugar Ray Leonard and RJJ are freakish flashy, gifted fighters who should get mentioned... But before those two would have to be Ali, Joe Louis, and Henry Armstrong... maybe even Langford and Duran... and Jack Johnson.
Well the word best to me translates to h2h matchups so with that in mind i'm saying the brown bomber. If ever there was a fighting machine not named sugar it was louis.
Tough one, but I'd say Armstrong. He was robbed of the middleweight title in his "draw" with Garcia, and had he won that one, he would have simultaneously held HALF the available world titles. Yeah, there were only eight weight classes then, but still............