I think it’s undeniable that Prince Adam, otherwise known as the Beast from Beauty and the Beast, has the most incredible eyes of any Disney prince.
It’s a plot point that his eyes are so identifiable. Belle recognises his eyes in the painting in the West Wing that he slashed when he was first turned into the Beast. As the Beast, the eyes are the only thing he has that hints at or even remains of his humanity. And then when the Beast transforms back into Prince Adam, Belle only has to look into his eyes to recognise him.
As for the princesses, I think Rapunzel has the most incredible eyes. They are larger than even your typical Disney princess, and a beautiful shade of green, a colour not often used. Rapunzel’s eyes are not a plot point, but I almost feel like they should be, since they are the same as a baby and as a young adult. There’s a mosaic of the baby Rapunzel in the city, and I’m pretty sure adult Rapunzel recognises something about her eyes being similar before she’s distracted.