Between the two I'd say Williard took a far worse beating than Frazier did. Dempsey was brutal and unlike George, he was allowed to stand over opponents as there was no neutral corner rule. But their fights were too short to consider them the worst. Tyson vs Douglas was a sustained beating that lasted 10 rounds. Vitaly vs. Briggs was also a sustained beating that should have been stopped sooner. Pacquiao vs. Margarito was another sustained beating Hopkins vs. Trinidad qualifies. Generally the longer the fight goes the worse off it is.
Indeed, sustained beatings are the worst. Holmes vs Ali was another one, with only Ali's amazing chin holding him on his feet.
calzaghe smashing lacy, but also the thriller in manilla ali frazier destroyed each other in that fight
Vitali vs. Danny Williams........... anyone? anyone? what was it, 5 knock downs and the ring was covered in blood?
Jerry Quarry v Joe Frazier I Corrales v Castillo Tua v Ibeabuchi Jerry Quarry v Norton...great performance by Jerry on short notice but... Morrisson v Foreman Holyfield v Foreman
based on these, willard took the worst beating all time wolgasts beating of nelson or grebs destruction of tunney rate pretty highly