Considering the fact that Iago is portrayed as a thoroughly wicked, manipulative man who is responsible for several characters's deaths in the play, one could surmise that Shakespeare had no intention of creating sympathy for his character. Unlike some of Shakespeare's other notable villains—like Shylock—Iago has absolutely no redeeming qualities, does not evoke a sense of pity or sympathy from the audience, and is portrayed as a completely vindictive, heartless villain. Despite the fact that Othello chose the inexperienced Michael Cassio over Iago, Othello's decision to promote the Florentine soldier to lieutenant does not justify Iago's treacherous actions. Even Iago's treatment of Emilia is despicable and portrays him as a debased, cruel husband. Iago's crimes also lead to the deaths of Desdemona, Othello, Roderigo, and Emilia, who are all manipulated by his villainy. It is safe to say that Iago does not deserve any sympathy, and the audience experiences pleasure knowing that he will be tortured as retribution for his awful crimes.
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. Iago 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!