Every super hero has a nemesis. Superman's is Lex Luthor. Lex Luthor is one of the most intelligent and richest men in the world. He owns most of Metropolis and most people in the city work for him in some way whether they know it or not.
He believes himself to be above the law and will bribe, sue or eliminate all who stand in his way and prevent him from getting what he wants.
Lex is secretly involved in many illegal activities which are often foiled by Superman's interference. He would like nothing more than to see Superman die by his own hand. Lex Luthor is an arrogant, jealous and ruthless man. In addition to Superman he hates many other super heroes as well, and often clashes with the Justice League.