I can only imagine the young Foreman vs Ruiz...hell, the Foreman that lost to Jimmy Young would have brutalized Ruiz.
When George wasnt in the mood to box, he'd just shove alot, and we'd all fly everywhere. I'll tell you, too; Being clinched up by Wlad Klitschko is like a kid wrestling their Dad. You feel impotent.
I picked young Foreman but Primo is an interesting call. I have sparring footage of him from the early '30s where floors a heavyweight and then scoops him up off the canvas like a child and sets him back on his feet, all in one movement. It was pretty impressive. I also have a clip of him in the 1920s training he takes a smaller fighter and holds up straight up over his head with one arm.
Of guys who won or fought for the championship, I'd say Primo Carnera had the most all-round strength.