In this kind of fanfiction, perhaps Harry, out of fear or some form of coercion, starts to obey Uncle Vernon's every order. Maybe Vernon uses threats about expelling Harry from the house or withholding food to make him submit. This could lead to a very different dynamic in the Dursley household, with Harry being more submissive and not showing his usual defiance.
Some writers might create this type of fanfiction to explore a different side of Harry's character. By making him submit, they can show his vulnerability in a new way. It could also be to create a more complex relationship between Harry and his Muggle relatives, adding a new layer of drama.
One possibility could be that Harry, out of a sense of duty or some form of magical coercion, decides to follow his uncle's every order in order to protect his aunt and Dudley from a new magical threat. He might suppress his own desires and instincts to keep them safe.
It could be that after a series of events that make Harry question his own judgment, he submits to Dumbledore's authority. For instance, if there are false prophecies or misinformation floating around that lead Harry astray. Dumbledore, with his greater experience and knowledge, helps Harry see the truth. So Harry decides to submit to Dumbledore in order to get back on the right track and protect Hogwarts and the wizarding world.
In this fanfiction scenario, it could be that the writer decided to change the power dynamics completely. Vernon, who is usually just a Muggle bully in the original, might be given some unexpected power or weapon in the fanfic. And Harry, perhaps caught off - guard or having lost his magic temporarily, could be killed by Vernon. It shows how fanfiction can turn the whole story upside down.
Well, perhaps Vernon might beat Harry out of his extreme dislike for magic. He could be enraged by some accidental magic Harry does at home and lose his temper completely.
In some fanfiction, Uncle Vernon develops by becoming more accepting. For instance, he may start to see Harry not just as a freak but as a person with unique abilities that can be useful. He might begin to tolerate the wizarding world a bit more, especially if he realizes that Harry can use his magic to protect the family from certain threats.
Maybe it shows how Harry endures the abuse from Uncle Vernon. It could explore Harry's feelings of helplessness and his thoughts during those tough times.
Some fanfictions might explore a backstory for Uncle Vernon. Perhaps he had an encounter with a wizard when he was younger that made him so bitter towards magic. In these stories, Harry could discover this secret and it could change their relationship. Also, there could be a plot where Uncle Vernon is magically turned into a wizard for a short time. This would be a comical yet thought - provoking plotline as he would have to navigate a world he once despised.
One possible motive could be his intense hatred for the wizarding world. Since Harry represents that world to him, he might murder someone he believes is part of the magic that he despises so much. Another motive could be fear. If he feels threatened by a magical being or situation, in his panicked state, he could resort to murder.
Hedwig could be one. She might fly off to get help, like to Hermione or Ron. They could then come up with a plan to rescue Harry from the Dursleys.