I'm not sure about best performance, but imo his best win, and it must be up there with his best performance, was vs Barney Ross. I rank Ross #15 all time p4p & he's typically in most credible top 20 p4p all time lists I've seen. At 28 Ross was an experienced veteran of over 70-fights who would have still been in his natural physical prime. He was the reigning WW champion, a division in which I rank him #16 all time based purely on fights contested in that division. Armstrong was the reigning FW champion and weighed under the LW limit. So, against the WW champion in his prime, who some 85-years later is still considered top 15/20 p4p all time, the reigning FW champion, outweighed by 8.5lbs, dominated, scoring multiple knockdowns and winning between 10 and 12 of the 15-rounds. This is one of the best wins and performances in boxing history, imo.
For me it has to be Ross, not many guys could smother and stop Ross from working the jab, but Armstrong took it away and made it an infight game.
I have a 20 min HL of most of the rounds, I did not see a knockdown in the film. Had Armstrong or Ross been knockdown in the contest, I am sure it would of made the cut.
