Well, in 'harry hates hermione fanfiction', it could be that the writer is trying to show how misunderstandings can lead to such extreme emotions. For example, perhaps there was a miscommunication about a spell or a magical event that made Harry wrongly think Hermione had betrayed him. Or it could be a way to explore how different personalities might clash more severely than shown in the original series, like Harry's impulsive nature conflicting more with Hermione's logical thinking.
One possible reason could be a miscommunication. Maybe Hermione accidentally reveals a secret of Harry's that he didn't want known, and this causes him to feel betrayed and start to hate her. Another reason could be jealousy. If Hermione gets more attention or praise for her magical abilities than Harry in the fanfic, he might develop feelings of envy and hatred. Or perhaps there's a love triangle situation where Hermione is involved with someone Harry doesn't like, and that causes his hatred.
One reason could be a divergence from the original character traits. In the original story, Hermione and Ron have a complex relationship with love and friendship. Fanfiction that misrepresents Hermione's feelings towards Ron might go against the essence of her character. Maybe the fanfiction portrays her as hating Ron in a way that doesn't fit with her growth and development in the official series.
Perhaps in the fanfic, there is a love triangle situation involving Ron. If Harry unknowingly gets in the way of Hermione's relationship with Ron, she could develop hatred towards him. Another aspect could be that Hermione feels Harry is getting all the credit for their group's achievements, while she is doing a lot of the behind - the - scenes work, which makes her resentful.
One reason could be that in this fanfiction's unique plot, there is a prophecy or some ancient magic that has been misinterpreted. This misinterpretation leads Harry to think that Muggle - borns are somehow linked to an impending doom for the wizarding world. So, as a result, he harbors hatred towards them. It could also be that there has been a series of unfortunate events that he wrongly blames on Muggle - borns, like a magical accident that he believes was caused by their 'uncontrolled' magic.
Perhaps in the 'harry hates dunbledore fanfiction', Dumbledore is shown as being involved in some sort of secret plot that goes against Harry's values. For example, if Dumbledore was secretly working with the dark side in the fanfiction, Harry would naturally hate him. Also, it could be that Harry has discovered some long - hidden truth about Dumbledore that completely changes his view of him, like a past misdeed that Dumbledore has covered up.
Maybe in that fanfiction, McGonagall has some actions that Harry misinterprets. For example, she might be too strict with him in a way that he can't understand at that moment.
It could be due to a misunderstanding. In the fanfic, Remus might say or do something that Harry misinterprets as being against him. For example, Remus could be trying to protect Harry but his actions come across as controlling, which would make Harry dislike him and potentially hate him.
Perhaps in this fanfic, the Weasleys have some actions that conflict with Harry and Hermione's values. For example, if the Weasleys were to make a deal with a dark wizard for the sake of their family's safety and Harry and Hermione found out. This could lead to a rift and hatred. Also, it could be related to a love triangle situation in a very convoluted way. Maybe one of the Weasleys unknowingly gets in the way of Harry and Hermione's relationship, or vice versa, which causes animosity.
One possible reason could be that the 'light' in the fanfiction represents something he associates with strict rules or a false sense of goodness. Maybe it has been used to manipulate people, and Harry, being perceptive, sees through it and thus hates it.
It could be a way for writers to show their creativity. By taking a well - known relationship and flipping it on its head, they can create unique and unexpected storylines. Maybe they want to explore how Ron would react to Hermione's hatred and how it would change his character development. Also, some fans might have their own personal interpretations of the characters that deviate from the original, leading them to write such fanfiction.