Smallville :

A glimpse of the future Lex Luthor is revealed after a black Kryptonite explosion splits Lex in two, and his evil side, Alexander, is released. Alexander immediately imprisons Lex in the mansion and begins his rampage by attempting to kill Clark and Chloe in the lab after they discover his secret, jousting with Lionel and convincing him to return to the dark side and, finally, threatening to close The Talon unless Lana moves in with him.

After discovering Clark's secret, he attempts to persuade Clark to join him. Clark uses black kryptonite to force the two Lexes back together.