Well, one possibility is that Harry would be raised in a very different magical environment. Bellatrix is a Death Eater, so he might be exposed to dark magic teachings from a young age. But perhaps, deep down, Bellatrix could have some strange maternal feelings towards Harry and protect him from the other more extreme Death Eaters. This could lead to a really complex internal struggle for Harry as he grows up, having to reconcile his own sense of right and wrong with the values he's being taught in Bellatrix's care.
In a fanfic where Harry is adopted by Bellatrix, it could start with Bellatrix having some ulterior motive for taking Harry in. Maybe she thinks she can use him as a weapon against Dumbledore or the Order of the Phoenix. Harry, on the other hand, would be in a constant state of fear and confusion. He would have to learn how to survive in Bellatrix's world. His magical abilities might develop in a different way too. He could learn some dark magic spells that he would later use against the Death Eaters when he finally decides to break away from Bellatrix's influence.
In such a fanfiction, Harry's life would be extremely different. Bellatrix is a Death Eater, so Harry might be indoctrinated into dark magic. However, his strong will from his original upbringing might resist this. He could be in a constant internal struggle between the light he was initially inclined towards and the dark teachings of Bellatrix.
In such a fanfiction scenario, Harry would likely grow up in a very different and dark environment. Bellatrix is a Death Eater, so Harry might be indoctrinated into the Dark Arts from a young age. His view of the wizarding world would be skewed towards Voldemort's ideology. He may also develop a more ruthless and aggressive personality, different from the kind - hearted Harry we know in the original series.
If Harry Potter was adopted by Bellatrix in fanfiction, his life would be completely different. Bellatrix is a Death Eater, so Harry would grow up in a very different environment from the one he had at the Dursleys. He might be indoctrinated with Voldemort's ideology. However, Harry also has his own strong will, so he could potentially resist Bellatrix's influence and try to find his own path in the dark world he's been thrust into.
Well, it could be that Klaus, with his complex and often dark nature, sees something special in Harry. Maybe he wants to use Harry's magic for his own purposes at first. But as time goes on, he starts to develop a real bond with Harry, like a father - son relationship. Harry, on the other hand, might be both intrigued and a bit scared of Klaus at the start. Then he grows to understand Klaus better and they face different challenges together, perhaps against other supernatural beings who are envious of Harry's power or threatened by Klaus's new protege.
One plot point could be the initial encounter. Harry might be on a mission related to Voldemort and come across Bellatrix. At first, they would be hostile towards each other, but then Harry sees something in her that makes him curious. Another point would be the development of trust. As they interact more, Bellatrix starts to open up about her past, like her family's influence on her path to the dark side.
One possible plot twist could be that Harry, under Bellatrix's influence, becomes a much darker and more ruthless wizard. Bellatrix might train him in the Dark Arts, and he could end up being a sort of anti - hero. He might have a completely different view of the wizarding world and be at odds with his former friends from Hogwarts.
His life would be full of danger. Bellatrix is a volatile and dangerous person. Harry would be constantly surrounded by dark magic and the threat of Voldemort. He might not get the same kind of moral guidance he got at Hogwarts. His identity as 'The Boy Who Lived' would also be in jeopardy as Bellatrix might try to manipulate that for her own or Voldemort's gain.
In this fanfic, perhaps Harry Potter is orphaned in a different way than in the original story. Goku stumbles upon him and, not really understanding the concept of magic at first but sensing Harry's good heart, takes him in. Harry would be introduced to Goku's friends like Bulma and Krillin. Bulma might be fascinated by Harry's magic and try to find a way to combine it with her technology. As for Harry, he'd have to adapt to a very different world. Instead of Hogwarts, he might train at Kami's Lookout. And his relationship with Goku would be one of a son - father figure, with Goku teaching him important values like never giving up and always protecting the weak, which would also tie in with Harry's own nature of fighting against evil in the wizarding world.
Well, in a 'Harry impregnates Bellatrix' fanfic, it might explore the chaos that would ensue in the wizarding world. Harry's friends would be horrified and confused. Bellatrix, being who she is, might have her own dark motives for allowing or even causing such a situation. It would be a very complex and disturbing story that would likely rewrite many established character traits and relationships in the 'Harry Potter' universe.
His character would be under great pressure. He might become more secretive and cunning as he tries to hide his true feelings. Since Bellatrix is so unpredictable, Harry would need to be on guard all the time, which could make him more paranoid than the normal Harry we know.