In the fanfic, it could be that Kami has a conflict with one of Naruto's allies, and Kami's actions against that ally make Naruto angry and lead to his hatred. For example, if Kami tries to punish Naruto's friend for no good reason, Naruto would not be happy with Kami at all.
One event could be if Tsunade refuses to help Naruto save one of his friends. Naruto is very loyal to his friends, and if Tsunade stands in the way of him rescuing someone dear to him, it might cause him to hate her. For instance, if she thinks the mission is too dangerous and not worth the risk for the village, but Naruto sees it as a matter of life and death for his friend.
In fanfiction, it could be that the Third Hokage favored certain ninja over Naruto for no good reason. For instance, giving more resources and opportunities to others while Naruto had to struggle on his own. This unfair treatment might be a reason for Naruto's hatred.
Perhaps the hunters always interfere in Percy's adventures. They might show up at the wrong time and disrupt his plans. For instance, Percy was about to rescue someone, and the hunters came and took over, but in a way that put the person in more danger. This would make Percy resent them. Also, if the hunters have some internal politics that end up affecting Percy negatively, like they accuse him of something he didn't do just to protect their own reputation, that could lead to his hatred.
One possibility is that Hestia took away something important from Percy in the fanfiction. It could be a magical item or a chance to achieve a great goal, which made Percy resent her.
In some fanfics, there could be a misunderstanding. Suppose Kushina did something that Naruto misinterpreted as harmful to him or his friends. This misinterpretation could lead to his hatred. For example, if Kushina was involved in a mission that Naruto thought put the village at risk, but in reality, she had no choice.
One consequence could be that Naruto leaves the village. He might go on a journey alone, seeking a new purpose away from the place that has caused him so much pain. This would be a major change from his original story where he was so attached to the village.
Maybe he got into a big fight with his friends during Christmas. It could be that they had different ideas about how to celebrate or some misunderstanding that made him sour on the holiday.
One possible event could be that Kurenai accidentally endangers one of Naruto's loved ones during a mission. This would make Naruto angry at her.
Well, it could be part of a grander plan. Kami might know of a future threat that only a girl - Naruto can defeat. By turning Naruto into a girl, Kami is preparing him for this upcoming challenge. It could also be a test of Naruto's adaptability. Kami wants to see if Naruto can handle such a drastic change and still remain true to his ninja way. And perhaps there's some sort of prophecy or prediction that involves a female version of Naruto, so Kami is just making it happen to fulfill that prophecy.
He may dislike it because he feels that it undermines the real struggles and achievements of the ninja. In fanfiction, things might be made too easy or unrealistic. He has fought tooth and nail for everything in his ninja life, and seeing it made into something that doesn't represent that in fanfiction would make him hate it.