Scarecrow could also be a main antagonist. His fear - inducing toxins could be a real problem for Harry. Harry would have to use his magic to counter the effects of the fear toxin and also figure out a way to stop Scarecrow from spreading it all over Gotham.
Another possible main antagonist could be Two - Face. His sense of justice, albeit a twisted one, would likely be at odds with Harry's more magical and morally - grey - area - free way of doing things. He might see Harry's use of magic as an unfair advantage and try to bring him down, especially if Harry's actions start to influence the criminal underworld that Two - Face is a part of.
Well, one possibility is that Harry could use his magic skills to fight the crime in Gotham. He might team up with Batman, with Harry using spells like 'Expelliarmus' to disarm criminals while Batman does his stealthy thing. Maybe Harry would be initially confused by Gotham's dark and gritty atmosphere compared to Hogwarts.
The nogitsune could also be a major antagonist. It thrives on chaos and mischief, and a powerful wizard like fem Harry Potter in its territory would surely draw its attention. It might try to possess her or use her magic for its own evil purposes.
Harry might meet some American wizarding families that have long - standing traditions different from the pure - blood families in the UK. These families could introduce Harry to new forms of magic and social norms within the American wizarding community. He could also meet American Muggle - born wizards who have their own unique stories of discovering magic in a different cultural context compared to what he's used to.
The Thalmor could be great antagonists. Their strict control over magic and their anti - human beliefs could put them at odds with Harry. They might see his different form of magic as a threat to their power in Skyrim.
One possible antagonist could be a corrupt wizard in a high - ranking position in the Ministry of Magic's financial department. This wizard might be trying to cover up his misdeeds and would see Harry as a threat to his scheme.
He could meet Scott McCall. Scott, being a werewolf, would be intrigued by Harry's magic. They could become friends and learn from each other. Harry could help Scott better control his werewolf side using magic, and Scott could show Harry how to survive in Beacon Hills' supernatural chaos.
He could meet French pure - blood families who have their own long - standing traditions. For instance, there might be a family that has a special connection to a particular magical forest in France. Harry might also run into French wizards who are experts in potion - making, as France is known for its fine potions in the wizarding world.
It could be the other Titans who don't want a half - wizard, half - Titan like Harry to exist. They might see him as a threat to their pure Titan bloodlines or their power structure.
The Death Eaters could still be the main antagonists. They might see Fenrir's new alliance with Harry as a threat. Since they once used Fenrir for their dark deeds, they don't want him to turn good and expose their secrets.