oooops - please ignore the spelling mistake in the title : )

Iago is, I think, Shakespeare's consummate villain. Nowadays, he would be termed a psychopath, a human being completely without a conscience. But he's so intelligent he can make other people think he's right, and thus he's doubly dangerous to what an ordinary garden-variety villain would be.

Richard III is a fascinating villain, the way Shakepeare wrote him. I can still quote by heart the first sixty lines of Act 1, Scene 1 which I think sum up perfectly the injury and pique RIII feels. Richard III may be a victim of "bad press" and historically was something else; but leaving that aside and considering only the way he was portrayed by Shakespeare, he's not pure evil but tragically complicated and utterly human.

Iago and Richard III are undeniably bad, but can Lady Macbeth be seen as a villain? What might be the definition of 'villain'?

thyrkas, in plays the villain is surly the main character and antagonist to the hero.
So Shylock is the villain in Merchant of Venice, both his Uncle and Mother are the baddies in Hamlet and Lady Macbeth is the stronger character and nastier person in the play who's name we don't mention.
And who was it that ordered Little Arthur's eyes to be popped out in King John? Probably the monarch himself, he has always had a bad press; so he must be another evil chap.
I can't say why I think this because the question sounds rather too much like a school essay title and I'm far too old to re-tread that path. :-)

Hmmm... guess I was wondering if the definition of a villain is set in cement or open to interpretation. Othello is duped and acts in villainous way, but is not a villain in the way of Iago. One never has sympathy for Iago, but one might be able to at least empathize for a while with Lady M. In reading some critiques of M, I never saw the word villain used for Lady M, but rather 'character', so I wondered if the definition of villain was quite well circumscribed and that she did not meet the criteria.

Richard the third indeed got bad press - the Tudors knew that they had to give some sort of reason why they took over. Shakespear was their mouthpiece in many plays. Besides, I always felt him more of a melodramatic villian (like Snidley Whiplash, for those old enough to remember).

Definitely Iago. He takes the trust of his friend, the confidance of his wife, and twists things to the end where Desdemona is dead and Othello is ruined. For what purpose? Because he could.

Richard III was framed!
Iago has no redeeming qualities-he is evil personified, and takes great satisfaction in the exercise of his manipulations. Aaron in Titus Andronicus is another one-I find that a much more disturbing play overall than Othello.

cc- Yes, Titus Andronicus is violent in the extreme, from beginning to end. I don't know if I would go see the play.

never seen it, only read parts of it-couldn't watch it!