I know that Chaos King has more impressive scans that are multiversal. But while Zero Hour Parallax destroyed only one universe, he still had the power to undo most of Anti Monitor's damage in Crisis on Infinite Earths. I think this battle should be close with the possibility of both combatants winning.
@sithlantern93: ummh no Eternity couldn't fight CK and death ran away from him.... Death one shot and destroyed the entire cancerverse, Galactus engine and Shuma gorath who are universal level. But she fled CK