It's possible that in the fanfiction, Zeus made a deal that put Percy or his loved ones in danger. For instance, Zeus might have made an agreement with an enemy just to maintain his own power, without considering the consequences for Percy and those around him. This would surely make Percy hate Zeus.
Well, it could be that in the fanfiction, Zeus's actions towards Percy's friends or family were not good. For example, if Zeus endangered them or was overly harsh. Percy is a character who values loyalty and justice, so he would hate Zeus for acting against those values.
It could also be about power. Percy might realize that with Zeus out of the way, he can reshape the world of the gods in a more just and fair way. He could believe that Zeus's rule is corrupt and that killing him is the only way to bring about real change.
One possible implication is that it could influence how Zeus views the modern world's perception of the mythological characters. If he likes Percy fanfiction, he might be more open to the new interpretations and ideas that fans have about the whole demigod concept.
Jason might hate Percy fanfiction because it often creates scenarios that he finds unrealistic or untrue to the original story. For instance, if the fanfiction pairs Percy with characters in a way that doesn't make sense in the context of the original series, Jason would likely be put off. Another factor could be that the fanfiction might over - sexualize Percy or other characters, which is something Jason would not approve of if he values the integrity of the original characters.
Fanfiction often takes creative liberties. In this case, it might be that the author wanted to explore new power dynamics and character interactions. If Percy was Zeus' brother, it would completely change the power balance in the world of the series. Percy's connection to the sea and Zeus' control over the sky could lead to all sorts of interesting plotlines, like joint quests or power struggles between the two 'brothers'.
It could be that the writer wants to explore the darker side of human nature within the context of these characters. By having Annabeth cheat with Zeus, they can delve into themes like betrayal, jealousy, and the breakdown of relationships. Additionally, some might be doing it as a form of rebellion against the 'perfect' relationship that Annabeth and Percy seem to have in the original, wanting to add a bit of chaos and realism to the fictional world.
It's possible that in the fanfiction, the Cullens are involved in some sort of betrayal. For example, they might side with someone who is against Bella. This act of betrayal would be a strong reason for her to hate them. In fanfiction, new storylines can be created where the Cullens' actions are not in line with what Bella expects or desires, which can result in her hatred.
One possible plot could be that the entire Greek pantheon is thrown into chaos. Percy might be seen as a huge threat, and other gods and goddesses would either try to hunt him down or form alliances with him out of fear or a desire for power. Demigods would be forced to take sides, leading to massive battles among them.
In the fanfiction, Percy's relationship with Zeus may develop gradually. Zeus, being a powerful and often aloof figure, might initially be distant from Percy. But as Percy shows his courage and abilities, Zeus could start to take a closer interest. This might lead to Zeus mentoring Percy in some ways, teaching him about godly powers and responsibilities.
In this kind of fanfiction, Percy might challenge Zeus over issues like the unfair treatment of demigods. For example, Zeus could be overly harsh on demigods who make minor mistakes while the gods themselves get away with much worse. Percy, being a hero, would stand up for his fellow demigods.