In the fanfiction, Naruto could have been possessed by some dark force. This dark - Naruto then starts to act in a very unpredictable and scary way, like randomly attacking people with great force. He might also have a really creepy look in his eyes, which scares everyone around him. The villagers who once knew Naruto as a friendly ninja would be shocked and terrified.
Perhaps Naruto discovers a new form of power that is so intense and uncontrollable that it causes him to emit an aura of fear. His friends and foes alike are frightened because they don't understand this new power. They are worried that Naruto might lose control completely and cause destruction, so they are all scared in the fanfiction.
His close friends like Sasuke and Sakura would likely be among the most affected. They know Naruto well and seeing him in a terrifying state would be very shocking for them. For Sasuke, who has a deep bond with Naruto, it would be especially hard to face a scary Naruto.
Maybe Naruto shows up with a new transformation that's not like any of his previous ones. In this 'fanfiction', it could be a form that gives him abilities that are far beyond what anyone thought possible. He might be able to fly without using any chakra wings or something similar, which would shock everyone.
One possible plot could be that Izuku has been through a really traumatic experience that has changed him. He starts to isolate himself and when people try to approach him, he acts in a way that scares them off. He could have developed some sort of survival - based aggression. For instance, if he was trapped in a really dangerous situation where he had to fight to survive, he might now react harshly to any sudden movements or people getting too close to him, which would scare his friends and classmates.
In some fanfiction, Naruto might be wanted by everyone during a time of rebuilding. His positive attitude and ability to bring people together would be valuable. For example, after a great war, villages might want him to help in establishing peace treaties and relations. Also, if there's a mystery that only he can solve due to his unique experiences, people would be seeking his help.
Another scenario could be when Batman is under the influence of some sort of dark magic or mind - control. He then uses his skills and knowledge against the League in ways they never expected. His sudden change in behavior and the fact that they have to fight a friend can be really frightening. Also, Batman might create a false apocalyptic scenario where the Justice League fails miserably. He shows them their weaknesses and how those could lead to the destruction of the world. This makes them question their abilities and scares them into re - evaluating their roles.
Perhaps in the fanfic, Izuku is possessed by some dark entity which changes his behavior and makes him do terrifying things, causing fear among his friends and foes alike. For example, his actions might be unpredictable and seem dangerous to those who know him. He could start speaking in strange voices or have sudden outbursts of strange powers that startle everyone. This would lead to a situation where everyone is scared of him, and the story could revolve around how he tries to get rid of this possession or control this new and scary side of himself.
In some 'naruto is attacked' fanfictions, he might be attacked by a new group of powerful villains who are not in the original series. For example, a secret organization that has been hiding in the shadows and finally decides to target Naruto because of his growing influence in the ninja world.
One interesting scenario could be Peter Parker teaming up with different superheroes in unexpected ways. For example, he might have a wild adventure with Doctor Strange where they have to travel through different dimensions to stop a powerful enemy. Another could be his interactions with the X - Men, like having a friendly sparring session with Wolverine and learning from his combat experience. And also, a scenario where he forms an alliance with the Guardians of the Galaxy and they all have to adjust to each other's very different personalities while on a mission to save the universe.
His classmates like Bakugo could be a main character. Bakugo might be one of the first to notice the strange changes in Izuku and could be both scared and angry about it. He might try to confront Izuku, which could lead to some intense scenes.
One scenario could be when Gaara is having nightmares about his past. Naruto shows up at his bedside and sits with him. He tells Gaara that he too used to have bad dreams but he learned to face his fears. Naruto then holds Gaara's hand and stays with him until he falls asleep again. Another scenario is when Gaara is feeling left out during a shinobi gathering. Naruto notices and drags him into the middle of the group, introducing him to everyone and saying how cool Gaara is. This makes Gaara feel more welcome.