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 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.
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.
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.
The cultural differences between Naruto's world and Rias's world could play a part. Naruto's world has a strong sense of community and loyalty within the ninja clans. Rias's world of devils has a more hierarchical and self - serving structure. These differences could cause Naruto to have a negative view of her in fanfiction.
One possible reason could be a misunderstanding. Maybe Anko was involved in a mission that Naruto thought was unjust, and he misjudged her actions as being malicious. For example, if she had to capture someone Naruto considered a friend, even if it was for the right reasons from Anko's perspective, Naruto might hold a grudge.
Perhaps Naruto feels that the Hokage has been too strict or unfair in dealing with certain situations. Like if the Hokage didn't support Naruto's way of trying to bring peace and unity, which Naruto firmly believes in. This could lead to a growing resentment and eventually hatred.
One possible reason could be betrayal. If Naruto was constantly let down or betrayed by those he trusted among humans, it could lead to his hatred. For example, if his friends turned on him because of his jinchuriki status.
It could be that Naruto has a different view of leadership than Sarutobi. Naruto might see Sarutobi's leadership as being too passive or too focused on maintaining the status quo. He, with his more energetic and revolutionary ideas, may resent Sarutobi for not being more progressive in making the village a better place for everyone, including himself.
Perhaps he blames ninjas in general for the loss of someone close to him. For example, if a group of rogue ninjas were responsible for the death of a dear friend or family member, it could make him resent the whole ninja concept. He might think that if there were no ninjas, such tragedies wouldn't occur.
One possible reason could be a feeling of betrayal. Maybe the Kages made decisions that Naruto thought were against the greater good or the well - being of the ninja world. For example, if they were too focused on protecting their own villages at the expense of others.