42) Superman is hit with a red-K laser again and this time it's permanent (who you give the powers to is up to you.)

43) Lois is furious with Superman in TOGOM and finds some Kryptonite to destroy him.

44) Superman accidentally kills while under the influence of magic in "Illusions of Grandeur" and decides to either retire Superman permanently or find some kryptonite to take himself out for the good of humanity.

45) Lois realizes during the scene where she speaks to him in "Barbarians at the Planet" that Superman is Clark Kent. Superman promptly dies of ecstasy.

46) Lois figures out how Superman "gave" his powers to Resplendent Man and publishes it out of spite. Superman goes into hiding/retirement (does this count as "Killing superman?" up to you.)

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.)