Whether or not the prince gets a redemption arc or not, I don't particularly care. What I do care about, tho, is that he stays firmly out of Melissa's "harem". Basically he can't have a redemption arc and try to romance Melissa (or keep their engagement) at the same time. So if he's part of her harem, he is irredeemable. Even if the author writes him having a redemption arc, if he's trying to romance Melissa, then I don't buy it