Iago: Shakespeare's Master Manipulator
Iago's evil nature stems from multiple sources of resentment that fuel his revenge plot. He wasn't chosen for promotion by Othello - instead, Cassio got the job he wanted, creating a burning jealousy that drives much of his behaviour.
His racial prejudice against Othello is clear from his declaration "I hate the Moor", reflecting the discriminatory attitudes common in Shakespeare's era. Iago also suspects that Othello slept with his wife Emilia ("He's done my office"), though this paranoia reveals more about Iago's insecurity than any actual evidence.
What makes Iago truly terrifying is his "motiveless malignity" - a phrase coined by critic Coleridge meaning he's evil simply because he can be. He takes genuine pleasure in others' suffering, describing his actions as "sport and profit" and planning to "enmesh them all".
Iago's manipulation tactics centre on appearing as "Honest Iago" whilst secretly orchestrating everyone's downfall. He convinces Roderigo to "put money in thy purse" and pursue Desdemona, uses this to fuel allegations against Othello, and systematically destroys lives whilst maintaining his trustworthy facade.
Key Point: Iago represents pure evil hiding behind a mask of loyalty - he's the villain the audience sees clearly, but other characters remain blind to his true nature until it's too late.