Harry's character would be very complex. He'd likely start off confused, as he's growing up with Voldemort. He might be conflicted between the dark teachings he receives and his own innate sense of right and wrong. As time passes, he'd probably become more rebellious against Voldemort's ideas, especially when he starts to learn about the real world outside Voldemort's influence.
At first, Harry might be a bit submissive to Voldemort, seeing him as a father figure. But as he witnesses the cruelty of the Death Eaters and Voldemort's actions, his Gryffindor courage would start to emerge. He'd become bolder in defying Voldemort's orders. He might also develop a more nuanced view of magic, understanding that dark magic isn't the only way, and he could start to explore other forms of magic secretly.
Harry's character would likely be a mix of confusion and determination. He'd be confused by Voldemort's teachings which go against his natural inclination towards good. But his determination to find his true self would remain. He might develop a sort of duality, acting one way around Voldemort and his followers, but secretly being someone else.
In this fanfiction, the relationship between Harry and Voldemort would be full of contradictions. Voldemort adopts Harry for his own purposes, but Harry has his own will. In the beginning, Harry may be forced to follow Voldemort's orders out of fear. As time passes, he might start to question Voldemort's actions and ideology. Voldemort, seeing Harry's growing independence, could become more controlling. This could lead to a cycle of rebellion and suppression in their relationship. Harry may also find some common ground with Voldemort in their shared loneliness or desire for power, which would add more layers to their complex relationship.
The plot might go like this. Harry is adopted by Voldemort and is made to believe that the wizarding world outside is full of enemies. But as he gets older, he discovers the truth about his parents' death and Voldemort's true nature. He then has to struggle with his loyalty to Voldemort who raised him and his sense of justice. He could use his unique position to gather intelligence about Voldemort's plans and eventually turn against him to save the wizarding world.
His character would likely be very different. He might be more cynical. Growing up with Voldemort, he would be exposed to a lot of dark and cruel things. He may start to question the concepts of good and evil as they are traditionally defined in the wizarding world.
He could develop a darker side to his personality. Learning from Voldemort, he may become more ruthless in achieving his goals, even if those goals are still ultimately good. For instance, he might be more willing to use unethical means to defeat other dark wizards. But at the same time, he would also be constantly struggling against this new - found darkness within him. He would be in a battle not just with external enemies but also with his own changing self.
Harry's character would likely become more hardened. Living with Klaus, he'd be exposed to a much more cut - throat world. His sense of morality might be challenged as Klaus has a different set of values. He could become more self - reliant too, as Klaus wouldn't coddle him. For example, in the wizarding world, Harry had friends to rely on, but with Klaus, he'd have to learn to fend for himself in different ways.
Harry's character would likely become more aware of different cultures. Growing up among the Cullens, he'd be exposed to vampire culture. This would make him more open - minded. He might also become more cautious, as vampires have different threats compared to the wizarding world.
He could develop new interests and skills. Since he's in a different family environment, he might be exposed to different hobbies or magical studies. For instance, if Dean's family has a tradition of potion - making in a unique way, Harry could pick up on that and become quite proficient, which would also boost his confidence.
His character would become more worldly. Since the Delacours are from France, Harry would be exposed to different values and ways of life. This could make him more open - minded. For example, he might be less rigid in his views on magic compared to when he was only in the British wizarding world.
His character would develop in multiple ways. Firstly, he'd become more resourceful. The Winchesters often find themselves in tight spots, and Harry would have to learn to use whatever he has at hand, including his magic, to get out of trouble. Emotionally, he might become more guarded as he realizes the harshness of the world they live in. But at the same time, he could also develop a stronger sense of loyalty towards the Winchesters, seeing them as his new family.