In The Lord of the Rings: The Return of the King, Éowyn kills the Witch-king of Angmar.
The Witch-king is the chief of the Nazgûl and the most powerful servant of Sauron. During the Battle of the Pelennor Fields, he confronts Éowyn, who has disguised herself as a soldier because women are forbidden from riding openly to war in Théoden’s host. Merry helps by stabbing the Witch-king with a blade from the Barrow-downs, weakening the spell protecting him.
Éowyn then strikes the fatal blow with her sword. The moment fulfills the Witch-king’s boast that no living man could kill him: Éowyn is not a man. The scene is often simplified as Éowyn defeating him alone, but Merry’s earlier attack is essential to the outcome. In Tolkien’s wider story, the prophecy’s wording and the special weapon work together to make the Nazgûl’s destruction possible.