By his reactions to certain situations. If there's a sudden noise or a surprise attack in the fanfiction, Naruto could over - react or freeze for a moment. This shows that there's fear lurking beneath his usually brave exterior.
His body language could show it. For example, he might tremble slightly, his hands could be clenched, or he could have a worried look on his face. This would be a simple and direct way to show his fear to the readers.
Another way to depict the fear is through their internal thoughts. The author could write in the first - person perspective for each character at times. Naruto might think about how the explosions remind him of the destruction he saw during the Pain invasion and how he doesn't want to see that kind of destruction again. Kiba could be thinking about how his ninja skills might not be enough to protect himself and his dog from the explosions. Issei might be having flashbacks to a past experience where he was nearly killed by an explosion and how that fear has now resurfaced.
In some Naruto fanfictions, Naruto's chaos powers might be shown as a wild and unpredictable energy source. It could make his jutsu more erratic but extremely powerful. For example, his Rasengan might become a chaotic, swirling mass of energy that can break through even the strongest defenses with ease.
One way is to show Naruto having nightmares about thunder. These nightmares could be so vivid that they start to affect his daily life. He could become more jumpy during thunderstorms, and this could lead to him making mistakes in his ninja training or missions. As the story progresses, his friends could help him deal with these issues.
In some fanfictions, Naruto's trauma might be shown through his nightmares. For example, he could be constantly haunted by memories of his lonely childhood, like the times when he was shunned by the villagers. These nightmares could disrupt his sleep and make him more on edge during the day.
Anko's possessiveness in Naruto fanfiction may be shown in the way she gets jealous easily. If Naruto gives more attention to another character, Anko might sulk or become angry. She could also be possessive in terms of protecting Naruto from perceived threats. Even if the threat is minor, she'll be very vocal and physical in her defense of Naruto, which shows her possessive nature.
In many such fanfictions, Naruto's power is presented as a guiding force for the younger generation. His skills and experiences are passed on, highlighting his lasting influence.
Another aspect could be that Naruto has a 'game menu' that only he can see. This menu would show his stats, his quests, and his relationships with other characters in a numerical or graphical form. He could strategize his actions based on the information provided in this menu, like choosing to focus on improving his relationship with a certain character to unlock a side - quest.
To write a 'fear naruto fanfiction', you need to understand the characters well. Consider their backstories and what might lurk in their subconscious that could be terrifying. For instance, Sasuke might fear being alone again after losing his family. Build a plot around this fear. Maybe there's a curse that isolates him from everyone. Also, use descriptive language to create an atmosphere of fear. Describe the cold wind, the dark shadows, and the eerie silence.
The fear might be manifested in the Kyuubi's attempts to negotiate with Naruto rather than fight. In fanfiction, the Kyuubi could offer Naruto things or make promises in order to avoid a situation where Naruto uses his power against it. This shows that the Kyuubi is aware of Naruto's strength and is scared of the consequences of going against him.
In some fanfictions, Naruto's inhuman strength might be shown through his ability to effortlessly defeat powerful foes that were previously unbeatable in the original story. For example, he could take on multiple S - rank ninjas at once without breaking a sweat.