It's possible that Natsu dislikes Fairy Tail fanfiction as it may change the dynamics between him and his friends. In the original, he has deep and specific relationships with his comrades. Fanfictions could rewrite these relationships in ways that he finds unacceptable, thus leading to his dislike.
One reason could be that the fanfictions don't match his view of the Fairy Tail world. He has his own understanding of the guild, his friends, and their adventures, and when fanfictions deviate from that, he doesn't like it.
One possible reason is the difference in power systems. Naruto has its chakra - based ninja abilities, while Fairy Tail has magic. Combining them in fanfiction might seem forced and not make logical sense to fans of Naruto.
One reason could be that the fanfiction author is trying to create a new and edgy storyline by making Natsu a more negative character. But this often doesn't sit well with fans who love the original positive and passionate Natsu.
They could leave for a quest of self - discovery. Natsu might want to learn more about his past, especially about his dragon, and Juvia could be looking to find out more about her water magic's origin. So they leave Fairy Tail to explore different places and meet various mages who might have the knowledge they seek.
Perhaps Natsu is under the influence of a powerful and dark magic that makes him lose control of himself and accidentally hurt Lucy. It could also be that Natsu is trying to protect Lucy from something but his actions end up causing her harm instead. Like if he tries to keep her away from a dangerous situation by pushing her too hard and she gets injured.
Maybe Natsu hates Fairy Tail fanfiction because he doesn't like how some fanfictions distort the original story or the characters. In the original Fairy Tail, he has a clear personality and relationships, and fanfictions might change that in ways he wouldn't like.
Sure, there may exist such fanfictions. In the official 'Fairy Tail' story, Natsu and Lucy are very close. But fanfiction is a world of creativity and deviation from the original. A writer might decide to make Natsu hate Lucy due to some made - up reasons like a misunderstanding or a conflict of interests. This could lead to a whole new set of adventures or conflicts within the 'Fairy Tail' universe as rewritten by the fanfiction author.
Well, it could mean that in a Fairy Tail fanfiction, the character Natsu is depicted as having feelings of hatred. Maybe the author of the fanfic has created a scenario where Natsu hates something specific like a particular character, a situation, or an event within the context of the Fairy Tail universe.
One possible reason could be a conflict with other guild members. Maybe there's a misunderstanding or a fight that makes Natsu feel he no longer belongs. Another reason might be that he has a personal mission that goes against the guild's rules or values in the fanfiction. He could also be framed for something he didn't do and, feeling betrayed, decides to drop out.
One possible reason could be a misunderstanding within the guild. Maybe someone spreads false rumors about Natsu, leading others to believe he's done something wrong. Another reason might be a power struggle. If there are those in Fairy Tail who envy Natsu's strength and popularity, they could plot against him to get him out of the way.
One possible reason could be to seek new adventures. They might feel they've reached a point in Fairy Tail where they've done all they can and want to explore new magic and challenges elsewhere. For example, they could have heard of a far - off land with a different type of magic that they are eager to learn about.