In the fanfiction, Susan might have a different ideology from Harry. For instance, she could believe in using dark magic for what she thinks is the greater good, while Harry is firmly against any form of dark magic. This fundamental difference can breed hatred.
One reason could be a conflict of interests. If they are competing for the same thing, like a magical artifact or a position in a magical society, and Susan uses underhanded tactics, Harry would hate her.
Another possibility is that there is some sort of personal misunderstanding between them. Maybe Susan Bones accidentally reveals one of Harry's secrets or makes a wrong assumption about him in public, which embarrasses Harry and leads to his hatred. Also, it could be that her family background or family connections play a role. If her family has some past issues with Harry's family or friends, it might fuel Harry's negative feelings towards her.
One reason could be the pressure. Harry is constantly under the spotlight during the tournament, and he may not like that kind of public scrutiny. In fanfiction, this pressure could be amplified to an unbearable level for him.
One possible reason could be his lingering resentment towards James Potter, Harry's father. Snape and James had a long - standing feud during their school days. Since Harry looks a lot like James, Snape might be transferring his old grudges onto Harry.
One reason could be competition. If Chloe is presented as a rival in the fanfiction, Ash might hate her for trying to outdo him in Pokemon battles or other aspects. For instance, if she constantly shows off her skills or Pokemon, it can make Ash feel annoyed.
One reason could be that he was treated unfairly by other shinobi. If he was constantly looked down upon or discriminated against by his fellow shinobi, it might make him develop a hatred for them.
One possible reason is that Naruto is so focused on his ninja training and his goals in the shinobi world that he views Christmas as a distraction. He might think it takes people's attention away from more important things like self - improvement and protecting the village.
It might be due to the way their goals are presented in fanfiction. Naruto is often about protecting his village and friends. If Artemis's goals in the fanfic are in conflict with Naruto's, like if she's more focused on her own self - interest in the story, Naruto would hate her.
It's possible that the writer of the fanfiction has given Akeno a backstory or personality trait that directly clashes with Naruto's. Maybe she is extremely arrogant and Naruto, who is humble and believes in everyone's potential, would find that detestable.
One reason could be that he doesn't like how some fanfiction writers misinterpret his character. They might make him act in ways that are completely out of character in relation to Renesmee. He has a certain image of himself and his relationship with her, and fanfiction can mess that up.
In some fanfictions, Peter could have a secret that he's keeping from the Avengers. When it's eventually revealed, they might feel betrayed and turn against him. It could be something related to his powers, or his past associations that the Avengers find unacceptable, thus resulting in their hatred.