Alexander "Lex" Luthor was the billionaire CEO of LuthorCorp. He has struggled with a dark history and a darker destiny. Lex is the son of Lionel Luthor and Lillian Luthor. He was the brother of Julian Luthor and the half brother of Lucas. He had a thick mop of red hair as a child but has been bald since age nine after being caught in the 1989 meteor shower.

In the final years of Lex and Clark's association, Lex finally and decisively turned to darkness. He abused his company's assets and resources to fund questionable and most likely illegal scientific research on cloning and alien intelligence. He also recently purchased Metropolis' main newspaper, the Daily Planet and named himself CEO. He has already used his authority to kill stories , fire reporters, and monitor employee's computer usage.

Lex Luthor has an estimated net worth of at least $48.6 billion. In the late spring of 2008 Lex discovered Clark's secret. Lex then placed the Orb in the console of the Fortress of Solitude causing it to collapse on him and Clark. Lex somehow survived the collapse, despite Clark not seeing him emerge from the remains of the Fortress. He was being kept alive via machines and was relying on the success of Project Prometheus. However due to the interference of Lana Lang, his outside connection to Tess Mercer was cut off and Prometheus was used on Lana instead. He planned revenge on Clark, Lana, Tess and Oliver for all they had done to him and the result was that Clark and Lana were split up forever due to kryptonite radiation and Oliver got revenge on Lex by planting one of his own bombs under the truck he was in, seemingly killing him.