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.
In this fanfic, Rias might betray Naruto because of a misunderstanding. Maybe she misinterprets Naruto's actions as a threat to her or her group. So, she decides to take preemptive action against him. This could involve things like spreading false rumors about Naruto, or even trying to physically harm him to protect what she believes is in danger.
If Rias betrays Naruto, she herself could potentially be the main antagonist. Since Naruto is usually seen as a protagonist, Rias' actions of betrayal would put her in direct opposition to him. Her motives and actions would then drive the conflict in the story.
Another plot could involve Sakura being forced to betray Naruto. Let's say an enemy captures someone she loves dearly, like her parents or Sasuke, and forces her to give information about Naruto in exchange for their safety. This would create a very complex and tragic situation for her.
In some fanfictions, Scott might betray Stiles by choosing the wrong side in a conflict. For example, if there's a power struggle between different supernatural groups, Scott could side with a group that has intentions harmful to Stiles or his family.
Well, it could be that Rias betrays Issei for power. Maybe she is offered something extremely tempting, like a high - ranking position in the devil hierarchy, which makes her turn her back on Issei. It could also be that she is forced to betray him under some sort of blackmail or threat.
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 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.
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.
Issei would probably first try to understand why Rias has betrayed him. If he finds out that she was forced or manipulated, he might try to save her. But if it was a conscious choice, he could become angry and vow revenge. He has a strong will, and this betrayal could fuel his determination to become stronger on his own.
In a 'naruto gets pissed off fanfic', one possible scenario could be that Naruto discovers someone has been slandering his friends behind their backs. He would get pissed off and confront the person directly, his eyes blazing with anger.