Well, if Harry were raised by Voldemort in fanfiction, it could lead to a really complex character development. Harry would likely grow up with a great deal of internal conflict. He might be feared by the wizarding world as he is associated with Voldemort. However, he could also potentially use the knowledge he gains from Voldemort to defeat him in a different way. He could have a unique understanding of Voldemort's weaknesses.
In such a fanfiction, Harry might become a very different person. He could be more in tune with the Dark Arts. Maybe he would have a skewed sense of morality, influenced by Voldemort's views. He might also be more powerful in the Dark Arts but struggle with his identity as he is constantly in conflict between what he's been taught by Voldemort and his own inner goodness.
If Hermione was raised by Voldemort in fanfiction, she might have a completely different personality. She could be more ruthless and power - hungry. Her magic might be used for more dark purposes. For example, she could be trained to be one of Voldemort's most powerful lieutenants, using her intelligence to plan his attacks and strategies.
In such a fanfiction, Harry might be raised with a very different set of values. Voldemort could try to mold Harry into his own image, perhaps teaching him dark magic. But Harry might also secretly hold on to his own sense of good. For example, he could use the knowledge Voldemort gives him to ultimately turn against him.
Well, he might become a super - powered wizard - avenger. He could learn combat skills from the likes of Captain America and also use his magic in a more creative way with the guidance of the Avengers. Maybe he'd even have a special Avengers - themed wand.
In such a fanfiction, Harry might grow up with a very different set of values. Slenderman is often depicted as a creepy and somewhat malevolent figure. So Harry could be isolated from normal society. He might be trained in skills that are not typical for a regular upbringing, like how to move stealthily or sense danger in an uncanny way.
Well, if Harry were raised by the Joker in fanfiction, his personality would likely be a complete contrast to what we know of him. The Joker's influence would make him unpredictable. He might not value life in the same way as in the original Harry stories. Instead, he could be more interested in creating chaos and playing cruel jokes on people, much like the Joker does. It would also change his relationships, as his friends in the original story would probably be very wary of him or even become his enemies due to his new, Joker - influenced behavior.
If Harry gives Voldemort the stone in fanfiction, it could be a very dark turn of events. Voldemort would likely use the stone to bring back his physical form more fully or perhaps gain some sort of immortality. However, some fanfictions might explore the idea that this act actually unites the wizarding community against Voldemort in a way that they hadn't been before. They might see Harry's sacrifice as a call to arms and fight back even more fiercely.
Well, it could be really strange. Harry might find some new perspectives on his enemies or himself. And Voldemort could get angry as he might not like how he is portrayed in some fanfictions. Maybe he'd try to change things according to what he reads.
If Harry Potter was adopted by Voldemort in fanfiction, it would be a very strange and complex situation. Voldemort is a very evil character, but he might see Harry as a tool or an heir. Harry could be exposed to the darkest magic and the inner workings of the Death Eaters. However, Harry's own strong will and the influence of his parents' sacrifice might still shine through, leading to a possible rebellion against Voldemort later on.
If Voldemort gets custody of Harry in fanfiction, it would be a huge deviation from the original story. Harry would probably be exposed to a lot of dark and cruel things. Voldemort could try to break Harry's spirit and make him abandon his values. There might be a struggle within Harry between the good he has been taught and the evil that Voldemort represents. And the wizarding world would be in even more chaos as Voldemort would have more control over the one person who was seen as the hope to defeat him.
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.