[Barney]

Interesting comparison. From what I can remember of the days when people used to teach me Shakespeare, the Shakespearian tragic hero was a good man who had a flaw that would eventually undo him. For example -
Othello's jealousy (possibly based on his insecurity at being an outsider), Macbeth's lust for power (driven by the fear of being emasculated by his wife, resentment of Duncan, his sense of entitlement, or a myriad of other interpretations) etc.

Iago/Gaunt can be seen as equivalents, leading people to indulge their darker sides and end up ruined. What I don't agree with is that Iago's victims had no choice, whereas Gaunt's did. I would say all are trapped by their own weaknesses. Even if those weaknesses are ostensibly not failings, but desirable qualities. Desdemona tirelessly presses Cassio's case for promotion to Othello, because she is "nice" and wants the best for everyone. Unfortunately her insisitence only fuels Othello's belief she must be having an affair with Cassio!