Who could be the main antagonist in 'Harry Potter in Another Dimension' fanfiction?

A group of rogue ninja from the other dimension could also serve as the main antagonists. They might be jealous of Naruto's power from his original dimension and want to steal it for themselves. They could be led by a charismatic and devious leader who has a personal vendetta against Naruto for some reason, like he believes Naruto will disrupt their way of life in the dimension.

Maybe it's a corrupted version of one of the gods from Percy's world who has gained even more power in this new dimension. They could be trying to spread chaos and destruction, and Percy has to stop them. This antagonist would know Percy's weaknesses from their time in the original world, which would make the conflict more intense.

It could be a corrupted version of one of the Fairy Tail members from the other dimension. For example, an evil Natsu who uses his fire magic for destruction and domination. The real Natsu would have to face his own dark self and find a way to defeat him without losing his own identity.

It could be an alternate version of Orochimaru. Maybe in this new dimension, he has achieved ultimate power and is using it to control the different ninja villages.

A powerful and corrupted duelist from a forgotten dimension could be the main antagonist. This duelist might have discovered a way to harness the power of the dimensional rifts for his own evil purposes. He could be using this power to create chaos and destruction across all the dimensions, and only the combined efforts of the heroes from different dimensions can stop him.

A possible main villain could be an ancient sorcerer from the new dimension who has been awakened from a long slumber. He's enraged that the wizarding world has been interfering with his dimension's magic, and decides to take revenge on Harry Potter's world. He has powers that are unknown to the normal wizarding world, like the ability to control time in his dimension, which makes him a formidable foe.

In an alternate dimension fanfiction, Neville Longbottom could take center stage. He could be the hero who rises up against the dark forces. Luna Lovegood might also be a main character, with her unique perspective on the alternate wizarding world. And we could also have new characters that are exclusive to this alternate dimension. For example, a Muggle - born wizard who has the power to control time, and he teams up with Harry and his friends to save the wizarding world from a new threat that emerged in this alternate reality.

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.

Voldemort could still be the main antagonist. Even if Demetri has some sort of connection or change in the fanfiction, Voldemort's overarching evil plans would still be a major threat to both Harry and Demetri, especially if Demetri tries to deviate from the Death Eaters' path.

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.