Hulk, Juggernaut, Gladiator, Herc, and Thor can all break adamantium. Probably Ironclad too, his strength is pretty much undefined, its his fighting ability and lack of mental toughness that lets the Hulk beat him. Ironclad would also be extremely useful in the tug-of-war since he can increase his weight to any level he wants. 616 Thing has never damaged adamantium...he attempted to break a wall of admantium/vibranium alloy just a few issues ago. He was able to damage Terminus' armor which is nearly as durable as adamantium and requires 100+ strength to damage. He also tore through the hull of a Beyonder's space ship, which was also highly durable.