Ohhhh, Iago is the BEST Shakespearean villain EVAR. I've heard him compared to Edmund in King Lear, but it's been too long since I've read Lear, so I don't know about that. However, I think Edmund, at the end of Lear, admits that he was wrong (?), and Iago makes no such admission.

...Iago swears to Janus? HOW DID I MISS THAT? What act?

*loves this play to itty bitty pieces; can you tell?*