In classical and traditional literature, the protagonist is the main character of the story while the antagonist is the character or group of characters who oppose the protagonist. Both words come from the Greek language, "protagonist" means first combatant, and "antagonist" means opponent or competitor. In the simplest terms, the antagonist is the bad guy to the protagonist's good guy.In literature, the antagonist may oppose the protagonist physically, as in battle or a fight, in a clash of wills or rivalry. In some cases, however, the delineation between protagonist and antagonist is not always as clear. There may be times when the antagonist may in fact be the protagonist, a character who fights against their own emotions, desires and inner conflicts. Examples of such characters include William Shakespeare's "Hamlet" and Christopher Marlowe's "Dr. Faustus."
There may be multiple antagonists who may or may not act in concert within any given story. Taking "Hamlet" as an example, the characters of King Claudius, the murderer of Hamlet's father and now husband to his mother, is the more obvious or direct antagonist. Laertes, the brother of Ophelia who actually poisons Hamlet in the end out of revenge, is another antagonist.