Fifth Element
Legend
Facepalm indeed. DR in that form only exists in 3E. Or 3.5 actually, isn't it? 4E's resistance doesn't work that way, and pre-3E there was immunity to certain types of weapons, but no damage reduction.There IS however a tradition of DR/-, and untyped damage.
But sure, yeah... we'll just ignore it ever existed to help your point in relation to an example concerning superman..
*facepalm*
But here you are, assuming that if the 5E rules text doesn't specifically rule out something from 3.5, then it must be so. You have no basis whatsoever for that assertion. Especially since we don't even have the actual rules text for the reaper ability, just the summary provided on the character sheet.