Who could be the main antagonist in a 'Harry Potter post apocalypse fanfiction'?

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.

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.

Perhaps a new dark wizard or witch who has infiltrated the Ministry of Magic and made sure Harry was sent to Azkaban. This antagonist could be working towards a bigger plan to take over the wizarding world and sees Harry as a major threat even when he's locked up.

It could be Voldemort. He might see Harry's new waterbending ability as a threat and try to find a way to counter it. Maybe he would seek out dark magic related to fire to oppose Harry's water powers.

It could be a new dark wizard who has risen to power. This wizard might see Harry as a threat to his plans, so he manipulates the situation to get Harry exiled.

Another possibility is a corrupted magical creature that has been influenced by dark magic from the 'sociates'. This creature could be intelligent and manipulative, causing chaos among the students at Hogwarts and the wizards in the 'sociates'. It would be difficult to defeat as it has unique abilities that are not well - known to either group.

Perhaps a group of dark wizards who think that by disrupting time, they can bring back the dark ages of wizardry. They target the Timekeeper as the only one who can stop them. They use dark spells and curses to try and stop the Timekeeper from fixing the time - related problems they create.

Maybe a dark wizard who has an interest in Harry's newfound inheritance. This antagonist could want to steal his powers or use him for their own evil purposes. They might see Harry as a key to unlocking some ancient and powerful magic that they've been seeking.

The minotaur itself could be the main antagonist. It's a powerful and dangerous creature, and if it's been set loose in Hogwarts or is guarding something that Harry needs, it would be a major obstacle for him to overcome.