How about 'Harry: Shattering the Magic Rules'? It gives a clear idea of what the fanfic is about.
Maybe he discovers a new form of magic while breaking the rules. It could be something that was forgotten or forbidden. He might then have to decide whether to keep it a secret or share it with his friends and professors. This could lead to a whole new adventure as he tries to understand and control this new magic, all while avoiding getting caught by the authorities.
It could be about Harry Potter finding a way to break or disrupt the magic in the wizarding world. Maybe he discovers a powerful spell or artifact that has the potential to shatter the existing magical order.
I'm not sure specifically as there could be many different interpretations in such a fanfiction. It might involve Harry Potter doing something that disrupts the normal magic in the wizarding world, like breaking a powerful spell that holds the magic system together or finding a way to nullify magic in certain situations.
Hermione Granger might also be a main character. Given her intelligence and knowledge of magic, she could be helping Harry in his quest to break magic. She might be researching ancient spells or looking for loopholes in the magical laws. Ron Weasley could be there too, providing support and his own brand of humor and loyalty as Harry undertakes this dangerous mission.
By creating humorous situations. For example, Harry could try to use a simple spell like Lumos but end up making the whole room explode with light. This kind of comical mishap can draw readers in.
In such a fanfic, Harry might accidentally break a lot of magical laws. For example, he could perform spells in the wrong way, leading to unexpected and chaotic results. Maybe he'd use a powerful spell without understanding the proper incantation or wand movement, causing magical backlash.
In this fanfiction, Harry Potter is the central figure. However, other characters could play important roles too. Dumbledore might be involved as he has great knowledge of magic and could either oppose or guide Harry in his attempts to break magic. And Voldemort could also be a significant presence, perhaps his actions or the threat he poses are what drive Harry to consider breaking magic in the first place.
One idea could be to explore the lives of minor characters in the Harry Potter universe. For example, you could write about the backstory of Neville Longbottom's parents before they were tortured into insanity. Another idea is to create a new magical creature and describe its interaction with the known wizarding world. Maybe a creature that lives in the Forbidden Forest and has a special connection to the trees there.
One idea is that Harry discovers a magical realm that is fueled by pure love for magic. Only those with a true passion for magic can enter. Inside, he meets magical creatures that teach him forgotten spells. Another idea could be Harry teaching younger students about his love for magic through stories of his adventures. He could inspire them to look at magic in a different way, not just as a tool but as a beautiful art form.
One idea could be that Harry discovers he has a unique magical ability that even Dumbledore doesn't know about. This ability could be related to his connection with the very essence of magic. For example, he might be able to communicate with magical creatures in a way no one else can, which leads him to uncover secrets about Hogwarts' past.