Hmmm... Tempus really superseded Luthor over the years to me, especially when they used Tempus in "Soul Mates." After that he became way more menacing than Luthor ever was to me.

CLARK: No. I'm just worried I'm a jinx.
JONATHAN: A jinx?
CLARK: Yeah. Let's face it, ever since she's known me, Lois's been kidnapped, frozen, pushed off buildings, almost stabbed, poisoned, buried alive and who knows what else, and it's all because of me.
-"Contact" (You're not her jinx, you're her blessing.)