Bernkastel
Reaper of Miracles
No, I believe the one killed by Doomsday was Modern-Age Superman. Silver-Age had unlimited super-strength and could move several worlds at once, unlimited stamina, super speed so fast that he could travel through time, unlimited invulnerability, enhanced mental process, super vision consisting of x-ray, heat, telescopic and microscopic, super hearing, flight, super-breath, super-hypnosis and a bunch of other super stuff that I'm too lazy to write down.
I'd put him too close to omnipotent. If I recall the only person that could stop him if needed be was the Spectre [he was like Z from Tenchi.] Now that I think about it I probably shouldn't have let Superman Prime through either.
Can you choose someone else?