Who could be the main villains in a 'Harry works for Torchwood' fanfic?

Well, one possibility is that Harry could use his magical skills to help Torchwood deal with otherworldly threats. For example, he might use spells to contain alien creatures that Torchwood has captured. Maybe he'd be the one to figure out how to close a portal that was opened by some malevolent alien force, using his knowledge of magic which is completely new to the Torchwood team.

It could be a group of rogue Death Eaters who have formed their own empire after Voldemort's fall. They might be more radical and have new, even darker plans for the wizarding world.

Maybe a group of anti - magic fanatics within SHIELD itself. They see Harry's magic as a threat and try to undermine him at every turn. They could be secretly working with external forces that also oppose the use of magic in the world of SHIELD. Harry would have to prove that his magic can be an asset rather than a liability.

There could also be a new group of supernatural beings, perhaps a cult that worships dark magic. They might target Hellsing because of their power and the fact that Harry, with his wizarding abilities, is now part of the organization. This cult could be trying to summon some ancient and extremely dangerous entity, and Hellsing, with Harry's help, has to stop them.

There could be new villains like an evil wizard - scientist who wants to use magic to create black holes and destroy planets for his own gain. Or perhaps an alien race that has a natural ability to drain magic from wizards and witches and they see the Hogwarts students as a source of power.

Some dark wizards who were in hiding during the main battle might emerge. They could see the post - battle chaos as an opportunity to gain power.

Ron could be Harry's ally as well. Despite his sometimes clumsy nature, he's loyal and has his own areas of expertise, like wizard chess which could be metaphorically applied to some strategic decision - making in the Ministry. Additionally, some of the younger, more progressive Ministry employees who are inspired by Harry's heroics could also side with him and be his allies in any changes or projects he undertakes within the Ministry.

One possible main villain could be an Egyptian wizard who has been corrupted by dark magic. He might be after some powerful Egyptian artifact that can give him ultimate power. He could see Harry as a threat to his plans because Harry has knowledge of different kinds of magic from Hogwarts.

It could be Death Eaters who have a new plan. They might want to create chaos in the Muggle world by targeting the Queen. They see her as a symbol of Muggle power and order, so by attacking her, they hope to disrupt the Muggle - wizard relationship.

The Malfoys could be the main villains. They might have turned to even darker magic after the fall of Voldemort and formed their own secret organization. Lucius Malfoy could be using his wealth and influence to gather dark wizards and witches to create chaos in the wizarding world.