I wouldnt class Ali-Foreman as a terrible beating (unless you meant Foreman-Frazier) but I agree that Ali gave Frazier a terrible beating in the last 2 rds of their 3rd fight.
Walcott - Marciano does deserve a mention. Rounds 11-12 were bad rounds were Rocky took a lot of punishment. Don Dunphy, "Marciano took such a terrible beating in rounds 11 and 12, I didn't think he was going to come out for the 13th round."