Maybe Naruto gives up because he faces too much criticism in the fanfic world. He might feel that he can't meet the high expectations of the fans.
Perhaps in the fanfic, Naruto is faced with a situation where he has to sacrifice something he really values in order to continue. And he decides that he can't bear that sacrifice, so he gives up. This could be something like giving up his relationships with his friends or his loyalty to his village in exchange for more power, but he refuses to do so and thus gives up on the path he was on in the fanfic.
It could be that Naruto in the fanfic has some sort of personal crisis. For example, he loses his confidence after a major defeat, and this leads him to give up on his ninja dreams or his role in the fanfic's story line. He might think that he is no longer fit to be a hero or to pursue his goals.
One possible scenario could be that Clary is in a situation where she has no one around due to some unforeseen circumstances like being stranded in an isolated place. Another could be that she chooses to be alone because she doesn't want others to see her in a vulnerable state during childbirth.
One possible scenario could be after Naruto loses a difficult battle. Hinata might find him sitting alone, looking dejected. She could sit beside him and start by saying how she saw his amazing efforts during the fight. Then she might share some of her own insecurities and how Naruto's determination has always inspired her. This would remind Naruto of his own importance and boost his spirits.
One scenario might be related to a failed mission. Maybe Naruto is sent on a top - secret mission that is much more dangerous than anyone anticipated. He could be betrayed by someone he trusts during the mission, leading to his death. Or perhaps there are some unforeseen circumstances, like a strange and deadly curse that gets unleashed during the mission which he succumbs to.
Maybe Naruto gets tired of always chasing after Sasuke. He has his own life and dreams too. He might think that he has sacrificed enough of his time and energy on Sasuke, and it's time to focus on himself and the village. He could start to believe that Sasuke has made his own choices and he can't keep forcing Sasuke to come back.
In a fanfic, Naruto might power up by having a spiritual awakening. He could connect with the spirits of past Hokages in a deeper way, gaining their knowledge and some of their power. This could enhance his existing jutsu and give him new abilities. Vegeta could power up if he were to face a near - death experience against Naruto. This could trigger a hidden potential within him, like a new type of Super Saiyan form that has unique abilities. He could also fuse with another Saiyan (if there were another Saiyan available in the fanfic's scenario) to create an even more powerful being.
It could also be due to a misunderstanding. Some false information might have spread in the fanfic's world, making Naruto believe that everyone has turned their backs on him. Like, some bad guys framed his friends, and Naruto, being unable to see through the lies at first, gives up on everyone in despair.
One possible scenario could be Naruto being constantly ostracized in the village. People might avoid him not just because of the Nine - Tails inside him, but also due to false rumors spread about him. For example, they could say he's a bad omen. This would lead to Naruto feeling extremely lonely and isolated, and he might start to train alone more often, distancing himself further from the possibility of making friends.
In this kind of fanfic, one possible scenario could be that Naruto leaves Konoha due to feeling misunderstood. Maybe he has been wrongly accused of something and decides that he can't stay in a place where people don't trust him.
Well, it could be that Rias betrays Naruto for power. Maybe she makes a deal with a powerful enemy of Naruto in order to gain more influence in the ninja world or some other realm. Another possibility is that she betrays him out of jealousy if Naruto has something she desires deeply, like a special technique or a strong bond with someone she wants to break.
Maybe in the fanfic, Naruto discovers that his parents' death was not as straightforward as he thought. If he finds out that some powerful individuals in the village were actually involved in a conspiracy that led to their deaths, this revelation could be the trigger for his descent into hatred. He might then turn against the village and its leadership, using his powerful jutsu not for protection but for vengeance.