Seldom mentioned is Hurricane Carter's one round knock out of welterweight Champ Emile Griffith. Bald headed Hurricane bouncing Griffith off the canvas. "No welterweight belongs in the ring with me" Carter said afterwards. Not sure what Griffith was doing up with the middleweights, ...he went back down and defended against Luis Rodriquez.
Think that had more to do with Carter's psyche job on Griffith before the fight, tearing him apart about being gay. Carter was a scary dude to begin with.
Any mention of McClellan vs. Jackson II? They waged war the first time, then the second time the first punch Gerald throws, he stuns Jackson, and then it's over. No one ever did that to Jackson before or after, and it wasn't even a give and take one round slugfest. McClellan just absolutely destroyed him.
Carter did a psyche job on Griffith no doubt, but it was nothing to do with Emile's sexuality. Rubin and Emile were friends and Carter stated that he told Emile he was not in that good a shape, thus Griffith did not give it his all in training and paid the price in the fight. Paret was the one who brought up Emile's sexuality.
Given the quality of the opposition, I would take Schmeling over Louis (1936) and Douglas over Tyson.
Were these upsets as huge as perceived in hindsight? Louis was in his second year as a pro going up against a former champion who was stylisticaly a more dangerous match than Carnera or Baer. Realisticaly he should only have been instaled as a 2/1 or 3/1 favourite. Tyson should only have been a 10/1 favourite over Douglas who was at least a live challenger.
I understood the question not as what was the biggest upset but what was the most awe-inspring destruction. Louis and Tyson were top tier talents beaten utterly and completely.
I would only consider Tyson vs Douglas in that case. Douglas completely dominated Tyson with the exception of 11 seconds in round 8. Louis had pretty good moments against Schmeling. If i remember correct, he had a pretty good 3rd or 4th round landing several combinations.
The first Schmeling fight, I belive Louis had a pretty bad 4th round. Being knockdown and takeing shots like that.