OK, we know this is unconventional, but hear us out. Leontes’s worst enemy and the thing that stands between him and happiness is his jealousy, which gives way to some pretty awful behavior toward friends and family. It’s not until Leontes repents (for sixteen years) and his “faith” is “awakened” that he can be reunited with his family and loved ones. So, in the first three acts of the play, Leontes’s flawed nature and bad behavior function as the play’s major “antagonist.”
In the second half of the play, it’s Polixenes’s turn to be the bad guy. When his son, Prince Florizel, falls in love with a seeming shepherd’s daughter, Polixenes is the man who stands in the way of the young lovers’ happiness. Good thing the lowly shepherd’s daughter turns out to be a princess – otherwise, Polixenes might have made good on his threat to scratch up her pretty face.