Often, writers will use Naruto's facial expressions to convey his emotions. His brows might be furrowed in distress, his lips quivering. And as he cries, he might clutch a memento, like a headband or a photo of his friends, which symbolizes what he's holding onto while feeling so broken. This shows his vulnerability and the depth of his pain.
One way is through detailed flashbacks. By showing past events where Naruto felt trusted and then contrasting them with the betrayal, it makes his emotions more vivid. For example, his relationship with Sasuke. If a fanfic shows how Naruto believed in Sasuke's loyalty and then the sudden shift when he feels betrayed, it can be very impactful.
They can show physical symptoms like sweating, trembling hands, or a racing heart. For example, Naruto could be in the middle of a meeting and start fidgeting with his hands and wiping his brow, signs that something's wrong.
Writers can show Naruto's worthlessness through his internal monologues. For instance, having him constantly think about his mistakes and how he's not as good as others. They can also use body language, like slouched shoulders and a downcast gaze when he's around other characters. Another way is to have him isolate himself, as if he believes he doesn't deserve to be around his friends.
They can show his vulnerability. Naruto is usually seen as strong and energetic, but with malnutrition, he can have moments of weakness, like fainting during training.
Writers often portray Hinata as a strong and determined character in the face of Naruto's darkness. She is usually shown as the one who stands by him no matter what. For example, she might be the only one who believes in Naruto when his dark side starts to take over. Hinata's shy nature in the original series can also be used in a different way. In fanfiction, it could be that her shyness is a mask for her inner strength which she uses to deal with Naruto's dark tendencies.
Writers also portray his struggle through his relationships. In fanfictions, Naruto may have difficulty opening up to people he cares about because of his abuse scars. He might push people away initially, fearing more rejection. For example, when Hinata shows her feelings for him, he may be hesitant to accept because of his past experiences of being unloved and abused, which makes for a complex and engaging character study.
Writers often portray their relationship as a mentor - mentee type. Mikoto, being an experienced Uchiha, can teach Naruto things about the ninja world and the Uchiha clan. For example, she could show him how to control chakra more effectively using Uchiha - style techniques.
They can describe his physical state. For example, 'Baby Naruto's face was red as he wailed, his tiny fists clenched tightly.' This gives a vivid image of how he looks while crying.
He could be feeling a sense of calm. Naruto has a certain presence that even in sleep can be soothing. Sasuke, who has had a tumultuous life, might find peace in just observing Naruto at rest.
Writers often portray Hinata as a strong - willed character. In the face of 'dark Naruto', she doesn't back down. For example, she might be shown as using her own skills and knowledge to understand what's wrong with Naruto. She is also depicted as very loving towards Naruto, which drives her actions in the story.