Alright I have to check out footage of Rosewall and Laver. I can't picture their backhands in my head.
It seems like all French players have nice one handed backhands. Maybe it's something in the water.
If Phillippoussis hasn't been mentioned his one hander was a cannon. I don't know if anyone had more pace than he did. I suspect some hit harder but I've never seen anything like it.