If Galento actually had a defence instead of relying on his chin. (His idea of defence was catching the punches with his head) Would he actually stand a chance against Louis? He did knock Louis down with a single punch in round 3. He certainly had a tremendous 1 punch power. He doesn't have to defeat just stand his ground for 15 rounds. He did wrestle an octupus and boxed with a kangeroo and a 550 pound bear.
Joe Louis is stronger than octopus, hits harder than a kangaroo kicks, and loads more skilled than most bears, except perhaps Wojtek and Yogi. The answer is no.
I think you are underestimating Tony his chin. He took a blow from Louis that lifted him of his feet, he could still stand up. The referee stopped because his face was turning into a bloody pulp. The first time he hit Louis right, Louis was for the reminder out of reach and went to his chair on wobbly legs. The second blow that really connected knocked Louis down. It was amazing that Louis could stand up so quickly, Louis was the much better boxer. But one punch power and chin should go to Tony. I don't think any fighter could have taken the combo of hits Louis gave Tony in round four.