Obviously, Naruto is the main character. He's the one who is going to transform into this badass figure. Sasuke might also play an important role. He could be Naruto's rival - turned - ally or vice versa. Their relationship always adds depth to the story.
Another possibility is that Naruto undergoes some intense training in a secret location. There, he meets a wise old master who teaches him ancient ninja techniques that have been forgotten for centuries. With these new skills, Naruto returns to his village and astonishes everyone with his new level of power and confidence. His new badass persona would inspire the younger generation of ninjas to strive for greater heights as well.
Well, perhaps Bella starts learning self - defense skills. She could train with a mysterious mentor and then be able to take on any threats in her world. For example, she might face off against some dangerous supernatural beings and defeat them with her newfound badassery.
It could be a powerful vampire who doesn't like Bella's new - found strength. This vampire might see her as a threat to their own power and control in the vampire world.
In 'bella becomes a badass vampire fanfiction', she could develop unique vampire powers. For example, she might be able to control the minds of other vampires. This would put her in a powerful position within the vampire world. She could also use her new status to change the way vampires interact with humans, making it more peaceful or something like that.
He becomes more aloof. Instead of being the overly friendly Naruto, he might be more reserved. For example, he won't immediately trust people like he used to.
One popular 'badass naruto harem fanfiction' is 'Naruto: The Harem King'. It shows Naruto in a more powerful and charismatic light while building his harem in an interesting way. The story has great character development for not only Naruto but also the girls in his harem.
I think 'Naruto: The Elemental Master' is a top - notch fanfic. Here, Naruto gains control over all the elements in a very unique way, which sets him apart from his canon self. The story has great pacing and the fight scenes are beautifully written. 'Naruto: Reborn as a Jinchuriki' is another good one. It gives Naruto a new perspective as he is reborn with the knowledge of his previous life. And 'The Legendary Naruto' is a fanfic that really amps up Naruto's badassery. It has him facing god - like enemies and coming out victorious through his sheer will and newfound powers.
In the Naruto x harem fanfiction, Naruto is a badass because of his combination of raw strength, strategic thinking, and his heart of a hero. He's not afraid to go against the odds and always finds a way to come out on top for himself and his harem.
Perhaps some of the other Cullen family members would be her allies. They are already vampires and could help her adjust to her new powers and the vampire lifestyle. For instance, Alice might use her power of seeing the future to guide Bella in making important decisions. Jasper could teach her how to control her new vampire instincts, like the urge to hunt. And Emmett could be her sparring partner to help her improve her combat skills.