Identifying the antagonist of Sir Gawain and the Green Knight is a little less straightforward than identifying the protagonist. For while it’s true that the Green Knight’s supposed desire is to chop Gawain’s head off with his axe, the beheading game, as it turns out, is really no more than a good-natured test. And the Green Knight doesn’t hold it against Gawain when he fails to return the girdle. He tells Gawain that since this failure wasn’t out of greed or lust, but only "because you wanted to live: so I blame you the less" (2368). Can we really call someone whose testing also teaches an enemy? Maybe not. But since he seems so to Gawain for most of the story, it’s probably safe to call him an antagonist of sorts.