Brainiac. Sick of Luthor.

Both are far too overexposed today, and in such shoddy, compromised "reimagined" versions as well...

Back when I could care, Brainiac was "cooler" being a "living computer," but the Pre-Crisis Luthor had so much more going for him...

I've got to give the nod to Luthor. The man could build the most fantastic devices using only a lens, a spring, and an orange juice can. Driven by wounded vanity and ego, with a blinding hatred of Superman, but not necessarily the rest of the world, he'd have been happy to cure cancer and solve the world economy once he watched his hated foe sicken, turn green, and die in agony. Classic villainy.