Iago is the main antagonist in William Shakespeare's tragedy Othello. He is a manipulative and scheming character who plots to ruin Othello's life by making him believe that his wife Desdemona is unfaithful. Iago is often considered one of Shakespeare's greatest villains due to his complex and multi-faceted personality. He is a master of deception, using his cunning and wit to manipulate those around him. His motivations are never fully revealed, leaving readers to speculate on his true intentions.