Leo Dorfman and Jim Mooney make Lex Luthor’s dreams come true in Action 298 (March 1963).
Supergirl’s attempts to get Luthor released into her custody, to help her against the Phantom Zone villains, fails. The warden thinks it is just another of his tricks. So when the villains offer to give him super-powers, and free Lena from Kandor, as long as he will help them kill Superman, he changes sides in a second.
Luthor constructs a device for Jax-Ur, General Zod and Kru-El that will draw down a gold kryptonite meteor from space. The villains plan on using it to remove Superman and Supergirl’s powers, and then kill them. But they also intend to kill Luthor right after.
Not realizing that Luthor could hear their plans with his super-hearing, they fall easily into his trap, as he gets Superman and Supergirl to pretend to be weakened by phony gold kryptonite. The villains then approach them with no fear, and are quickly taken down.
Luthor, who lost his power belt in the climactic fight, agrees to return to prison, as long as they release Lena from Kandor.
Ironically, considering that this all began with Lesla-Lar, no one else ever really learned what she was up to, or the extent of her actions.