Which action most makes Creon a villain in this story?

remaining the king of Thebes

placing revenge above sacred duty

honoring Eteocles for defending Thebes

making proclamations after the war

Creon is the brother of Jocasta and so is the brother-in-law and uncle of Oedipus, in the play he is the king of Thebes that gives the throne for Oedipus and his sister hand to Oedipus when he deciphers the Enigma of the Sphinx.

What most makes King Creon a villain in the trilogy of Oedipus Rex is placing revenge above sacred duty.

After Oedipus death when Antigone's goes back to Thebes she found her brothers, Polynices and Eteocles dead after fighting a war, and Creon which has taken the throne of Thebes refuses to give Polynices the right to be buried as punishment for he being a traitor, but gives Eteocles the right, honouring him for defending Thebes. Antigone claims this to be a right given by the Gods for human and bury herself without Creon permission the body of Polynces. She is sent to prison and kill herself, her fiancée Creon's son kills himself too, devastated with this all Creon's wife also takes her life leaving Creon by himself.

The answer is placing revenge above sacred duty.