In this fanfiction, Voldemort is an obvious villain. But there could be other threats. There might be an ancient order within the assassin world that has its own dark agenda and sees Harry as a tool or a threat. They could try to manipulate him or kill him to further their goals. There could also be some wizards who are against the idea of a wizard - assassin hybrid. They fear that Harry could disrupt the balance between the wizarding and non - wizarding worlds. These characters would oppose Harry not just because of his power but also because of what he represents.
Well, aside from Voldemort, there might be corrupt elements within the assassin organization that raised Harry. They could see his magic as a threat to their power and secrecy. Also, there could be some dark wizards who team up with the assassin enemies of Harry. These villains would be more complex as they combine the danger of dark magic with the stealth and combat skills of assassins. And there could be a new character, perhaps an assassin who was once a friend but turns bad due to jealousy or a thirst for power, creating a more personal and dangerous threat to Harry.
Voldemort would still be a likely villain. He is the main antagonist in the original series and his threat to Harry is always present. Even if Harry is trying to save himself, Voldemort's power and his desire to kill Harry would make him a formidable foe.
Voldemort would still be a major enemy. But with Kratos raising Harry, Voldemort might face a much more challenging opponent. Also, any dark wizards or creatures that oppose Harry would be in trouble. Kratos wouldn't tolerate any threats to Harry, so even the Death Eaters would have to be extra careful. Another potential enemy could be those in the wizarding world who oppose Kratos' methods of raising Harry, seeing them as too brutal or un - wizard - like.
Obviously, Harry Potter himself. Then there could be a Texan version of Hagrid, like a big - hearted rancher who discovers Harry's magical abilities. There might also be a local witch or wizard who acts as a mentor, someone with a thick Texan accent. And don't forget about the muggles in Texas, Harry's classmates at a regular school before he goes to Hogwarts. They could be curious, tough - as - nails Texans who don't quite understand Harry's strange behavior at times.
Obviously, Harry himself. Then there could be German - born wizards and witches who become his friends or mentors. There might be a strict German potions master like Snape in Hogwarts. And perhaps a German - version of Dumbledore, an old and wise wizard who guides Harry.
In such a fanfiction, apart from Harry, there could be a gang of street urchins. One of them might be a girl who has a special connection with Harry. And then there are the professors at Hogwarts. Snape would probably have an even more difficult time with this street - raised Harry. He might see him as a troublemaker at first. And Dumbledore would be the one trying to guide Harry in this new, different situation, still seeing his potential.
Some of the Death Eaters who might have survived or changed their ways in an alternate universe could be the slashers. They would bring their knowledge of the Dark Arts and their own twisted view of the wizarding world. Bellatrix Lestrange, if she had a different path, could be a very interesting slasher figure in such a fanfiction, as she is extremely powerful and unpredictable.
In the wizarding world, there might be some jealous wizards who don't like Harry's unique combination of powers. They could team up with dark forces, maybe some Death Eaters who are still lurking around, and try to bring Harry down. They might be envious of the attention Harry gets or fear his new - found powers will disrupt the traditional ways of magic.
One potential villain could be Voldemort from the Harry Potter world. He might see Harry's new alliance with Erza as a threat and try to destroy it. Also, there could be villains from Erza's world who are jealous of the power that Harry and Erza together possess.
It could be really exciting. Harry might grow up with stealth and combat skills. Maybe he'd use his assassin training to fight the dark forces in the wizarding world in a very different way from the original story.
In this kind of fanfiction, Harry might grow up with a very different set of values. He could be trained in dark magic or used as a tool by the villains. Maybe he would be more cynical and less trusting compared to the original Harry. For example, if he was raised by the Death Eaters, he might be taught to hate Muggles and Muggle - borns from a young age.