I'm always a bit hesitant with this one because 'Fandeltales: The Cursed Prince' never had a single, straightforward antagonist in a traditional sense. The story sets you up to think it's the witch Elara who cursed the prince, and honestly, for the first two-thirds of the book, that's exactly what I believed too.
Then the twist hits where you realize Elara's 'curse' was actually a desperate protection spell against the real rot, which was the prince's own father, King Alistair. His greed and ambition to conquer the neighboring fae woods—using dark magic that slowly consumed his own son—is the actual core conflict. The 'villain' is this legacy of poisoned ambition, which makes the prince's internal struggle way more compelling.
That being said, my last re-read made me sympathize with Elara even more, and I'm not convinced the king is purely evil either, just tragically misguided.
Honestly, depends on how you read the moral shades.