Bio: Years of carrying around kryptonite in his pocket gave
Luthor something unexpected--a form of Kryptonite poisoning, something
only those who're exposed it for extended periods of time get. Luthor
was forced to go to prison after his attempted murder of
Superman--something that was only foiled by an implication of his
poisoning--a severe chest pain knocked him an unconscious state and
crashed the plane. There, he teamed up with Ultra Humanite. The two
escaped from prison but ultimately got thrown back in again, when their
attempts to form an Injustice Gang were foiled.
Lex returned again to take sides with a super-soldier type of a being,
called Amazo. After tricking Amazo into doing his dirty work and
destroying the Justice League, Amazo copied all of the Justice League's
powers, and when he fell onto J'onn J'onzz mind-reading capability, he
was able to find out what Luthor's true intentions were. Amazo spared
Luthor's life and flew off into space, and has yet to be seen again...
Luthor later got a pardon later on for helping the Justice League
"power-down" their alternate selves, the Justice Lords, and said in a
press conference that he's done with his ways of wrong-doing and was no
longer excited by the day-to-day riggers of the business world, but was
looking into a more challenging field, politics.
For more, refer to the Justice League Unlimited bio.