Comic book character owned by DC Comics. The most famous cueball in comics, Luthor has been Superman's archenemy for decades.

When he was introduced, back in 1940's Action Comics #23, Lex had a mop of red hair, but he lost his hair not long afterwards when one of the artists mistook a bald-headed assistant for Lex himself. During the Silver Age, Luthor was a scientific and criminal genius who held a grudge against Superman -- years ago, when they were both kids in Smallville, Superboy accidentally caused Luthor to lose all his hair.

In the post-Crisis DC universe, Luthor is the ruthless CEO of LexCorp International, one of the largest corporations on the planet. Until Superman showed up, Luthor was the most powerful and most popular man in Metropolis, but after the Man of Steel caused several of Luthor's schemes to go bad, he devoted himself (and the vast monetary and technological resources of LexCorp) to destroying Superman. He hasn't succeeded yet, and Superman knows he's up to no good, but he hasn't been able to prove that Luthor is anything other than the benevolent philanthropist he pretends to be.

In late 2000, Luthor was elected President of the United States of America. He was considered a fairly competent president, but he was still obsessed with using the vast might of his office to try to destroy Superman. In time, he went crazy, went openly supervillain, and got kicked out of office. But later, he convinced everyone that it was all the fault of an evil doppelganger. He isn't president anymore, but he's still running his megacorp as a secret "Get Rid of Superman" enterprise.

(Thanks to super-comics-historian Timeshredder for some of Luthor's history...)