Believe it or not Joe Frazier. Most see him as a face first brawler. But he was very hard to land on cleanly, Ali missed a lot more punches than he landed on him. Ali was the fastest heavyweight in history when both hands and feet are considered. Joe Frazier who was usually the aggressor in all of his fights, for that type of fighting style was very hard to hit. Julio Chavez Sr, and Henry Armstrong fits the same bill. Aggressive fighters , that one would think should be relatively easy to hit, but wasn't. Chavez had excellent head movement in his prime , was very good with blocking and parrying punches. Armstrong was very good at smothering opponents offensive output by staying close to them.
Absolutely. For his style of fighting Frazier's defense was most impressive. The Futch drills and advice improved it greatly. Armstrong was a master at getting his head into area's the opponent couldn't take advantage of when chest to chest........where Armstrong was almost his entire career. Chavez backed up a great chin with solid defense.
Duran's defense has been rated brilliant in here for well over a decade. During his career a lot of people missed this trick but they caught on, eventually. Of all people bob Arum knew how little punishment he wore all the way past SRL.
I was JUST about to post something about Joe Frazier on this thread until I saw your comment--you beat me to it LOL!! (But you stated exactly what I was going to say--Frazier's bob and weave was VERY deceptive and he was not an easy fighter to land a clean shot on.)