In this kind of fanfic, perhaps Harry has finally had enough of the Dursleys' mistreatment. He might use his magic in a moment of rage. Maybe he starts by levitating Dudley to teach him a lesson after one too many taunts. Or he could use a spell to make Aunt Petunia's precious china smash, as a way of getting back at her for all the years of neglect and cruelty.
The main characters are Harry, who has reached his breaking point with the Dursleys. His pent - up anger and frustration towards them finally explodes into action. The Dursleys, on the other hand, are the recipients of Harry's wrath. Uncle Vernon, with his blustering and bullying ways, Aunt Petunia, who has always been cold and distant, and Dudley, the spoiled brat. There could also be appearances from characters like Dumbledore, who might show up to either reprimand Harry or offer some kind of guidance depending on the nature of the attacks.
In this fanfic, Sirius could be tipped off that the Dursleys are planning to send Harry away to some even worse place. So he swoops in. They flee to a remote wizarding village. There, Harry meets other wizards and witches who are sympathetic to his cause. Sirius helps Harry train in combat magic, as he anticipates future battles. Harry also gets to explore his magical heritage more freely without the Dursleys' restrictions.
Well, perhaps Daphne somehow discovers Harry's awful situation at the Dursleys. She might use magic to break into the house secretly. Then she could use a spell to make the Dursleys forget about Harry so that she can take him away without a fuss.
It could be that a non - human magical being, like a centaur or a house - elf with a strong sense of justice, takes Harry from the Dursleys. They might see the abuse and neglect he endures and decide to act. This could lead to Harry having a completely different perspective on the magical world as he's exposed to aspects of it that are not typically part of a human - centric view.
In this fanfic, the Potters could have faked their deaths all along. They come back to rescue Harry when they find out how horribly the Dursleys are treating him. They might bring some magical creatures with them to help. For example, a phoenix that can heal Harry if he has any injuries from the Dursleys. Then they take Harry with them on a magical journey to a hidden wizarding community where they can all be safe and happy.
Well, one possibility could be that the Dursleys suddenly realize Harry's importance and the power he holds. They might see how he could bring them some sort of status or protection in the wizarding world. So, they start to accept him, change their attitude towards him, and perhaps even help him in his magical studies in secret.
In some interpretations, it could be that Harry finally snaps after years of abuse from the Dursleys. Maybe they pushed him too far one day and in a fit of rage, he uses his magic to end their lives. It's a very dark and extreme take on the Harry Potter universe.
The plot twist could be related to Snape's true motives. He might be under an Unbreakable Vow to rescue Harry from the Dursleys. In the process, Harry realizes that Snape is not as bad as he seems. This could lead to a complete change in their relationship. Harry could start to trust Snape, and Snape, in turn, could teach Harry some unique magic that he has never learned before, which is crucial for the upcoming battle against Voldemort.
Perhaps in this fanfic, Severus doesn't just save Harry physically from the Dursleys. He also saves Harry from the emotional and psychological damage that the Dursleys have been inflicting on him. Severus, having his own traumatic past, might be able to relate to Harry on a deeper level and starts to mentor him in ways that Dumbledore never could. This could lead to a completely different Harry, more confident and less impulsive.
Perhaps Harry uses his influence among his friends. Hermione could help him find some loophole in the Muggle - wizarding laws regarding property. Ron might provide some comical support, like trying to use some half - baked spell to make the Dursleys uncomfortable enough to leave. In the end, Harry evicts them and takes over the house, turning it into a place that's more welcoming for himself and his wizarding friends when they visit the Muggle world.