The Othello Adversary is Iago, a four-letter word. Iago is a fictional character in William Shakespeare's play Othello. He is the play's main antagonist, and is known for his manipulative and deceptive nature. He is a soldier who serves under Othello and is jealous of him. Iago plots to ruin Othello by falsely accusing his wife Desdemona of infidelity. He is considered one of Shakespeare's most complex villains.