Who could be the main antagonist in a 'Harry Potter Alter Universal King' fanfiction?

It could be an alternate version of Dumbledore. Maybe in this universe, Dumbledore has been corrupted by power and his thirst for knowledge leads him to do dark things. He could be trying to control the entire wizarding world using some powerful and forbidden magic.

Well, it could be about Harry Potter finding himself in an alternate universe where he is a king. Maybe he has to deal with different magical politics and power struggles that are far more complex than in his original world. He might have to form new alliances and face new enemies all while trying to figure out how this new world's magic works compared to his own.

It could be a powerful dark wizard who wants to control the spiders for his own evil purposes. He might see Harry as a threat to his plans since Harry is the 'King of the Spiders'. This wizard could be using dark spells to manipulate the spiders and turn them against Harry and the wizarding world.

Maybe it's a rogue group of wizards who fear Harry's power over Dementors. They might think that Harry is going to use the Dementors to take over the wizarding world in an unjust way. So they band together to try and stop Harry before he can fully embrace his role as the King of Dementors.

It could be a dark fairy who is jealous of the Fairy King's alliance with the wizarding world. This dark fairy wants to destroy the connection and take over both the fairy realm and the wizarding world.

Another option could be a corrupted version of Merlin. What if he was turned evil by some dark magic? He would know all the secrets of both the Arthurian and wizarding worlds. He could use this knowledge to create chaos and try to rule over both. Harry and the good knights of Arthur would have to find a way to reverse his corruption.

Perhaps a long - lost relative of the Potter family who feels they were unjustly excluded from inheriting the manor. This relative could be jealous of Harry's status and the wealth associated with the manor. They might use dark magic to try and claim what they think is rightfully theirs, leading to a battle of magic and loyalty within the Potter family and among Harry's friends.

Well, in an Alter Universal Fanfiction, there could be a scenario where the Sorting Hat sorts students based on different criteria. For example, instead of sorting by courage, intelligence, etc., it sorts by potential for a new kind of magic. Also, Voldemort could be a hero in this alternate world. He might have been misjudged in the original timeline, and in this new universe, he uses his power to fight an even greater evil. Additionally, the houses in Hogwarts could have different alliances. Maybe Gryffindor and Slytherin form an alliance against a new threat.

Maybe there could be a new antagonist, a dark shapeshifter who is jealous of Harry's power. This antagonist could be an old wizard who has been in hiding for centuries, waiting for the right time to emerge and take over the wizarding world. He sees Harry as a threat to his plans and tries to eliminate him.

Another possibility is a corrupted member of the Ministry of Magic. They might be trying to use Harry as a scapegoat to gain more power within the Ministry. They could be working with the Death Eaters or acting on their own, but they would be a significant obstacle for Harry as he tries to stay alive and free while on the run.