This is a surprising question. It would take a very sympathetic person to feel any sympathy for Iago at all. Are we supposed to feel sorry for him because he is such a wretched soul that he inflicts pain and suffering on other people? That would be a new way of looking at Shakespeare's play. Othello causes the deaths of Roderigo, Desdemona and Othello, and finally he stabs his own wife. He ranks with Richard III as Shakespeare's greatest villain. Watching or reading the play, we are appalled by his treachery and continuously hoping that someone will expose him before it is too late. I can only construe your question as having some kind of religious implication, such as the idea that we ought to do good to those who injure us and pray for those who spitefully use us. I don't think it was Shakespeare's intention for his audience to have any such feelings for Iago. I have never felt any sympathy for him, even after he was exposed and destined to be tortured unmercifully before being executed. But it's something to think about!