The Mutant Leader is a formidable adversary in 'Batman: The Dark Knight Returns,' a graphic novel by Frank Miller. As the ruthless and brutal head of the Mutants gang, he poses a significant threat to Gotham City. The Leader embodies chaos and violence, challenging Batman's return from retirement. His physical prowess and lack of morality make him a dangerous opponent. The Mutant Leader's conflict with Batman serves as a catalyst for the Dark Knight's resurgence, highlighting themes of justice, order, and the struggle against societal decay.