An antagonist is a character or force in a story that opposes the main character, known as the protagonist. This opposition creates conflict, which is essential for driving the plot forward. Antagonists can take many forms, including villains, rival characters, or even societal pressures. In literature and film, the antagonist's role is to challenge the protagonist's goals and values, often leading to a struggle that highlights the protagonist's strengths and weaknesses. Examples of antagonists include Darth Vader from Star Wars and Iago from Othello.