The way Hyperion killed Namor was so bogus. Yes I expect a powerful eyebeam could cut through normal skin like thru butter but Namor's skin is not normal skin, his skin and muscle should be the equivalent of trying to cut thru reinforced steel. In order to be able to cut Namor's head he would probably have to be immobilized to a platform and require Hyperion to be a long arduous time trying to do it not the way it happened, just a simple zzzzit! and his head is off!