The Canterbury Tales: The Miller's Tale
Nicholas and Absolon
If we (sort of) accept John as the protagonist, then Nicholas has to be the primary antagonist, with Absolon a close second. John's goal is to keep his wife to himself; Nicholas and Absolon desire only to thwart that goal. But what if we think Nicholas is actually the protagonist, as the "Booker's Seven Basic Plots Analysis" for comedy suggests? In that case, the primary antagonists become Absolon and John, who stand in the way of the hero and heroine's togetherness.