Superman and Lex Luthor have been enemies since the 1940s, when Superman first appeared in comic books. Lex Luthor is a criminal mastermind and one of Superman's most dangerous adversaries. The crossword solutions for the term 'Superman, to Lex Luthor' are 'ENEMY' (5 letters) and 'NEMESIS' (7 letters). Both words refer to someone who is an ENEMY or rival, and they both accurately describe the relationship between Superman and Lex Luthor.