Allying with Superman to defeat General Zod in Last Son, including personally gunning down one of Zod's men.
"I always wondered how it would feel to kill a Kryptonian. Feels pretty good."
In Justice League: Unlimited, he tricks Superman into leveling a Luthor-funded housing project. On national TV. With Captain Marvel standing up for Luthor, and publicly quitting the League over Superman's apparent vendetta. Even Lex was surprised at how well his plan went.
In perhaps the ultimate example of Moral Event Horizon meeting CMOA, blowing up New Krypton, and subsequently, using the reanimated corpse of a Kryptonian god to devastate Zod's army during War of the Supermen.
In 2000, Lex successfully turns his charity efforts in both Metropolis and Gotham into a winning bid to become President with Superman unable to do anything about it. He remains a thorn in the side of both Superman AND Batman (he framed Bruce Wayne for murder) while simultaneously becoming an international hero in the wake of Our Worlds at War. The Bad Guy Wins, indeed. He lasted almost a full term before the lead-up to Infinite Crisis drove him mad and pulled him from office.
During his time as the President Elect, Luthor is visited by Batman who demands that Luthor reliquish the Kryptonite ring he carries around if he's going to serve as the President of the United States. Luthor refuses and basically sends Batman running with a threat to use every resource at his disposal as President to hunt down and destroy Batman and his loved ones unless he leaves.
Luthor: Listen to me carefully, Batman. Because this is the only warning I'm giving. Echeclon. Keyhole. DEO. NSA. CIA. FBI. They're all mine, now. It takes one word from me, and I can dedicate this nation's power to your discovery. Or your destruction. I can spy on you 24 hours a day from orbit. I can learn all of your secrets, and Robin's, and Nightwing's, even that new Batgirl of yours. All of them, Batman. And there's nothing you can do. Leave. And the next time I see you, it had better be at the pleasure of the President or else I'll destroy you.
The animated Luthor avoids repeating the trick with his own display of awesomeness by mounting a $75 million Presidential campaign simply to distract Superman and the Justice League from his scheme to become a Physical God.
Luthor: President? Do you know how much power I'd have to give up to be President?
His cameo in Swamp Thing, in which he charges an enormous sum for five minutes of his time, deduces a method of destroying the godlike Swamp Thing in about four of those minutes, and explains that he left the remaining time so his employers could cut him a check. The device was so effective, the Swamp Thing had to beam its consciousness to another planet light years at the very last moment just to survive the trauma and was actually presumed dead by the people of Earth and the Swamp Thing's own masters!
Better still, when Swampy returns, the plant elemental murders every last person involved in the conspiracy in the first place... except Luthor, whose involvement Swamp Thing doesn't even suspect. In one of the Pre-Crisis Luthor's last moments, he's an effortless Karma Houdini.
Superman vol 1 #149 was an awesome moment from his point of view, even if it was an imaginary story: He manages to cure cancer... and kill Superman for real. No Brainiac, Zod, Doomsday, Parasite or Metallo. Lex Luthor murdered Superman, and he never came back from the dead. To add insult to injury, Lex forced Lois, Jimmy and Perry to watch while he killed him, he never grabbed the Villain Ball (he checked that his Death Trap worked fine, and he never left Superman's side or turned the Kryptonite ray off until he was completely sure that Kal-El was dead) and he would have gotten away with his crime if it wasn't for Supergirl. However he didn't know that she existed, so it was not his fault.