Admittingly, I have always been a rather harsh critic of Joe louis for facing men who's size dimensions would render them as being little more than Cruiserweights in a modern era.
One fighter whom I grossly over looked was Buddy Baer. He was 6'61/2" and weighed anywhere from 235 to 250 Lbs, making him larger than Gerry Cooney. In 50 pro victories, he won 45 of them via knockout. According to wikapedia, Baer is ranked by the ring magazine as being one of the top 100 heavyweight punchers of all time. What's more, in 57 pro bouts, he was only stopped on two occassions, one of which, against Louis. In their first meeting, Baer managed to floor Louis before going on to lose by disqualification. In their second fight however, Louis destroyed baer in a single round. After the fight, Baer proclaimed " the only way I could have beaten Joe that night was with a baseball bat. "
I've never actually sat down and watched footage of Buddy Baer, and don't know what his ring skills were like, but his credentials certainly sound as though he'd be tough for anyone on paper.