There's a fanfic called 'Nagisa's Assassin's Creed'. It shows Nagisa in a world of assassins, where she has to navigate through various challenges and prove herself. The story has a lot of action scenes that highlight her badassery.
One example could be that he had a epic fight scene. He was outnumbered but still managed to hold his ground. He used his agility and strength in a really cool way. Maybe he was dodging attacks with ease and then counter - attacking with powerful blows. This kind of scene would show his badass nature.
When writing a character analysis of Nagisa in relation to the ribbons on her wrist, start with her physical connection to them. Do they make her stand out in a crowd? Then, analyze her emotional bond. If the ribbons were given to her by someone she loves, it could show her loyalty and sentimentality. Look at her actions in the fanfiction. If she uses the ribbons to help others, it indicates her selfless nature. Also, consider how she might change over the course of the story because of the ribbons, whether she becomes more assertive or more withdrawn.
A fanfic could focus on a what - if scenario. What if Tomoya had met Nagisa earlier in their lives? Maybe they would have formed an even deeper bond from a younger age. They could have shared more childhood memories and their relationship might have developed in a different, yet equally beautiful way.
I'm not entirely sure specifically about 'nagisa no visual novel' without more context. It could potentially be a visual novel centered around a character named Nagisa. Visual novels often have storylines involving relationships, personal growth, and various adventures.
In these fics, Sakura often becomes badass through intense training. She realizes that she needs to be stronger to change things in Konoha or to prove herself. For example, she might train under a mysterious master or in isolation, like in 'Sakura's Solitary Training' where she spends months alone in the forest, honing her skills.