One common theme is self - discovery. Harry has been under Dumbledore's guidance for so long that when he breaks free, he has to figure out who he really is without that influence.
There's also 'Breaking the Bonds' in which Harry discovers some secrets about Dumbledore that make him lose trust. He then breaks free by leaving Hogwarts and traveling the wizarding world on his own, learning new magics and making unexpected alliances. This fanfic really focuses on Harry's character growth as he becomes more self - reliant.
One reason could be a misunderstanding. Maybe Harry discovers something that he misinterprets about Dumbledore's actions or plans. For example, if he finds out about some of Dumbledore's more secretive dealings in a way that makes him seem untrustworthy at first glance.
One possible plot could be that Dumbledore, perhaps under the influence of a dark spell, turns against Harry. He might try to prevent Harry from achieving his destiny in the wizarding world. For example, he could spread false rumors about Harry to turn the wizarding community against him.
Well, in this kind of fanfiction, Dumbledore himself would be the main antagonist since the title implies that he is the one 'breaking' Harry. He would be acting against Harry's well - being and goals.
In the fanfiction, Snape could protect Harry from Dumbledore by using his skills in potions. For example, he might create a potion that hides Harry's magical signature from Dumbledore's detection. Or he could use his knowledge of the Dark Arts to counter any spells or charms that Dumbledore might use to keep tabs on Harry. Snape is very intelligent and resourceful, so he could find various ways to physically and magically shield Harry from Dumbledore.
One possible reason could be that Harry has discovered something about himself or his past that he thinks Dumbledore might not approve of or might try to stop him from exploring further. For example, if he found out some dark magic connection in his family history that he wants to understand on his own without Dumbledore interfering.
One reason could be that Snape has his own complex sense of loyalty. He may feel that Dumbledore's plans for Harry are too dangerous or not in Harry's best interest in some ways. He has a long - standing relationship with Harry's mother, Lily, and perhaps through that connection, he wants to safeguard Harry from any harm that might come from Dumbledore's actions or decisions.
His friends might be initially divided. Some may be more loyal to Dumbledore's ideas and methods and might not understand Harry's decision right away. For example, Hermione, who often respects authority and tradition, could struggle with Harry's choice.
His friends like Ron and Hermione might help him. They are always there for Harry and if they believe that Harry has a valid reason for hiding from Dumbledore, they would likely do whatever they can to keep him hidden and safe. For instance, Hermione could use her intelligence to create spells or distractions to keep Dumbledore off Harry's trail.