I think Viscera was worse. besides Mark Henry was awesome as chocolate love or something like that, and he is an olympic gold medalist as the strongest man.
His demonstrations of strength were ok, but nothing that one wouldn't be able to see at a circus side show. As a character he was mediocre at best doing the chocolate love bit, but he has no wrestling skills whatsoever. Sure he can do power moves like some suplexes and various slams, but he can only do them one at a time. He can't do any highspots, sequences, counters or combos. There were even times that he couldn't take a bump well. Viscera is bigger than Henry, and yet he's still more agile and quicker than Henry is, so you don't (or I didn't at least) get as board watching his matches since he wasn't as much of a slow, lumbering mass.
If you want to talk about awesome big men, there's Bam Bam Bigelow, Earthquake, Typhoon, and even King Kong Bundy. Big, massive, yet quick and quite agile for men of thier size. If Henry could have brought his skills up to thier level, he could've dne so much better and been a much bigger star.