Maybe the Ministry's interference in Hogwarts affairs. Harry had a strong connection to Hogwarts, his school. If the Ministry started imposing unfair rules or regulations on the school, like controlling the curriculum in a way that restricts students' learning of real magic or defense against the dark arts, Harry would surely be against it and develop hatred for the Ministry.
One possible reason could be the Ministry's corruption. In the original series, we saw some Ministry officials being more concerned with power and image than doing what was right. They often turned a blind eye to real threats like Voldemort's return in the beginning. So in the fanfiction, this corruption might be exacerbated, leading Harry to hate the Ministry.
The Ministry's treatment of certain magical creatures could also be a factor. If they were mistreating creatures like house - elves or werewolves, Harry, who has a big heart and a sense of justice, would be outraged. He might see the Ministry as an unjust institution that doesn't respect all forms of magic and magical beings, thus hating it.
He might openly oppose their policies. For example, if the Ministry tries to pass a law that restricts the use of certain spells for self - defense, Harry could publicly speak out against it, giving interviews or writing articles in wizarding newspapers.
One possible reason could be jealousy. Maybe the sister is getting more attention from their parents or at Hogwarts. For example, if she is a star student and Harry feels overshadowed.
One possible reason could be a misunderstanding. Maybe Lupin did something that Harry misinterpreted as betrayal or negligence. For example, if Lupin was forced to keep a secret from Harry for his own safety, but Harry found out in a way that made him feel deceived.
One possible reason could be that fanfiction often takes creative liberties that may distort the complex character of Snape that J.K. Rowling created. Snape has a very intricate backstory and personality in the original series, and fanfiction might simplify or misinterpret it.
One possible reason could be that in the fanfiction, her parents might have made a sacrifice that left her alone, and she resents them for not being there for her. Maybe she feels abandoned and that has led to her hatred.
One possible reason could be that he might feel abandoned. Growing up without them, he could resent the fact that they left him an orphan. He might think that if they were really so great, they would have found a way to survive and be there for him.
Well, it could be that the two come from very different fictional universes with distinct magic systems and cultures. Harry Potter's world is based on a more European wizarding society, while Odin is from Norse mythology. Their values and the way magic works might clash in the mind of the fanfiction writer, leading to this 'hate' concept.
One possible reason could be feeling neglected. Maybe his family was always preoccupied with other matters, like protecting the village, and didn't give him enough attention. So he grew to resent them.
One possible reason could be the way he was treated as a child. He was ostracized and shunned by many villagers because of the Nine - Tails inside him. This constant rejection and coldness from the people around him might have led to his hatred in the fanfiction.
One possible reason could be that his family in the fanfiction might be cruel or neglectful towards him. Maybe they constantly put him down or don't support his dreams and ambitions, which would lead to his hatred.