Who could be the main antagonist in a Percy Jackson x Goddess Lemon fanfiction?

Perhaps an old enemy of Percy's from his demigod days who has now allied with some dark forces. They see Percy's transformation into a goddess as an opportunity to get revenge. They could try to corrupt Percy's new powers, for example, if Percy turns into Athena, they might try to make him use his wisdom for evil instead of good, causing chaos in the world of the gods and demigods.

Another possible antagonist could be a rogue demigod who is corrupted by the power of Chaos. This demigod might envy Percy's connection to Chaos and decide to turn against him. He could form his own group of followers, causing chaos (literally) in the demigod world. They would oppose Percy and his friends at every turn, believing that they are the rightful heirs to the power of Chaos.

It could still be Voldemort. Since he is the main villain in the original Harry Potter series, in this fanfiction he would see the Goddess Lemon as a threat to his plans of taking over the wizarding world. He might try to eliminate her before she can fully use her powers to help Harry and the Order of the Phoenix.

A powerful water nymph could be the main antagonist. Maybe she's jealous of the special bond between Percy and Poseidon and the power of the lemon. So she tries to steal the lemon and use its power to take over Poseidon's domain.

A good antagonist could be a powerful and vengeful centaur. Centaurs are known for their knowledge and combat skills. This centaur could have a grudge against both Percy, perhaps because he defeated some of the centaur's friends in the past, and the Hunters of Artemis because they protect the forests that the centaur wants to claim for his own evil purposes.

The goddess Hera might also be a great antagonist. Since she has a history of interfering in the lives of demigods, she could be jealous or threatened by Percy's rebirth. She might try to stop him from reaching his full potential in his new life or cause trouble between him and his new allies.

A powerful demigod who has been corrupted by the idea of primordial power could be the main antagonist. They might believe that by allying with a primordial or obtaining their power, they can become greater than the gods. This demigod would then oppose Percy, who stands for the protection of the current order.

An ancient and forgotten god who has been awakened. This god could be angry at the modern demigods for ignoring the old ways and decides to send assassins after Percy as a warning to the rest. They might want to bring back the old order where gods were feared and worshiped more and see Percy as a symbol of the new, more independent demigods.

Perhaps an ancient and dark deity who has been awakened due to some event related to Percy's exile. This deity wants to bring chaos to the world of gods and demigods, and Percy, even in exile, is the only one who can stop it. The deity would use all kinds of dark magic and minions to oppose Percy and his friends.

A new and powerful Titan could be the main antagonist. This Titan could be jealous of Percy's immortality and see it as something that should belong to Titans instead. He could gather a new army of monsters and try to overthrow the Olympian gods once again, with Percy being the biggest obstacle in his way.