
Camilo P. answered 07/05/19
Instructor of English with 10+ Years of Experience
I don't disagree with Heather. It is also worth noting, however, that, technically, an antagonist is simply someone or something which is opposed to the protagonist, or main character in a play. The protagonist does not have to be perfect, although Aristotle (and Shakespeare, probably), would insist that he or she must be noble, and this is the case with Macbeth, at least, who seems to have been relatively pleased with his station in life until this sudden opportunity for advancement presented itself.
I think we can all agree that Macbeth is the protagonist of this play, around whom the action revolves and in whose fate the audience is most invested. So I would not describe him as an antagonist, strictly speaking, nor a villain, neither, since he clearly fits the classic notion of a "tragic hero" brought down by some inherent flaw in his personality (i.e., ambition). [For a Shakespearean play that features a true villain as its protagonist, see, e.g., Richard II.] Lady Macbeth is a more complicated case, because I don't think we are ever given a sense that she is genuinely noble or good ... from the start, that is, she's presented as almost cartoonishly wicked. She may be one of the play's villains, as noted by Heather, though she is not, I would argue, an antagonist in the genuine sense of that word (since she and her husband are on the same page).