If he just stood there then the death spore power should eventually affect Superman. I'm totally talking out of my butt since I can't think of someone comparable that Omega Red has actually fought on panel. I'd say Supeman feels weekened by the life force drain but that's it. Ya he's immune to just about every type of disease but this is a pretty unique mutant power.
Before you eat me alive I did say it was a bit of a silly thread.