Fair, the actual character since it's vague and doesn't show much info, or at the least don't know if it has feats and abilities of both. While actual fusion, you know mostly everything about him already.
Well you kind of expect the intelligence and prep time of doctor doom, then the physical strength and unique evolution ability of doomsday would make him unstoppable.
Doctor Doomsday.
Skilled user of Superior Superpower Replication.
