In some fanfictions, Harry might show off his strong friendships, like his bond with Hermione and Ron. This could make Voldemort jealous as he has no such loyal comrades. Voldemort is often alone in his pursuit of power, while Harry is surrounded by people who love and support him.
Another way is through Harry's ability to love. Love is a power that Voldemort doesn't understand and can't possess. If in the fanfiction, Harry's love for his friends, family, or even the wizarding world in general is shown in a very strong and positive light, and this love gives him strength, Voldemort, who is cold and heartless, might be jealous of this power that Harry has that he can never have.
One possible scenario is that Harry masters a new and powerful form of magic that Voldemort has been unable to attain. For instance, if Harry discovers a way to combine different branches of magic in a unique way that gives him an edge in battles. Voldemort, who has always been obsessed with power and being the most powerful wizard, would surely be jealous of Harry's newfound abilities.
She might act overly friendly with other guys. For instance, she could be really touchy - feely with them, like hugging them a bit too long or playfully hitting their arms. This would make Harry jealous as he wants her attention all to himself.
Well, it could be that Voldemort spoils Harry in fanfiction by taking away his normal life. Voldemort might use his power to isolate Harry from his friends at Hogwarts. He could put spells on the school or the people there to make them shun Harry. This would not only make Harry lonely but also disrupt his growth as a wizard and a person.
Maybe Harry uses some powerful and unexpected spells. For example, he could combine the Patronus Charm with a blasting spell. The Patronus might distract Voldemort while the blasting spell hits him hard.
In this fanfiction, Voldemort's character is explored in a way that challenges our traditional view of him. His seeing Harry abused might make him reevaluate his relationship with Harry. He may start to see Harry not just as the Boy Who Lived who he wants to defeat, but as a person who has suffered, much like he might have in his own way. Harry, on the other hand, is stripped of some of his heroic facade. His abuse makes him more relatable in a sense. We can see his pain and how it affects his actions and decisions, and also how he reacts to Voldemort's new - found interest in his situation.
It might start with Voldemort's initial curiosity. He realizes Harry is more than just a threat. So he begins to observe Harry closely. As time goes by, Voldemort may start to feel a strange sense of connection, like he's the only one who truly understands Harry's power.
Well, in such fanfiction, Voldemort's possessiveness might show through his constant attempts to control Harry's actions. He may try to isolate Harry from his friends and allies, wanting Harry all to himself in a very dark and twisted way. For example, he could use dark magic to keep Harry in a certain place or manipulate situations so that Harry has no choice but to be near him.
It could start with a lot of animosity on Harry's part, but as he is trained, he might start to see Voldemort in a different light. Maybe he begins to understand Voldemort's motives, though not necessarily agreeing with them.
In this fanfiction, it could be that Voldemort has a premonition. He sees that if Harry Potter dies, it will lead to a series of disasters that will also destroy his own plans. So, in order to preserve the balance or to keep his long - term goals intact, he saves Harry. For example, if Harry's death causes an uncontrollable chaos in the wizarding world, Voldemort's rule over the dark forces might be disrupted. So he steps in to save Harry.
Perhaps in some fanfictions, Percy is given important tasks or missions that Harry feels he should have been assigned. This can make Harry jealous as he might think he is more capable or has more of a right to those opportunities. Another situation could be when Percy is praised for his leadership skills while Harry is still trying to figure out his own leadership style. It makes Harry feel overshadowed.