Obviously, Bella is one of the main characters since it's about her being a badass. There might also be other characters from the original story she is from, like Edward or Jacob, who could be involved in the new storylines around badass Bella.
Well, it depends on how the fanfiction is written. But surely Bella is the central figure. If it's related to a series where she has friends or foes, they could be in it too. For instance, if there are vampire or werewolf characters in the original, they might play important roles in the fanfiction, either as allies or antagonists to badass Bella.
Obviously, Bella is one of the main characters as it's named after her. There might also be other characters like her friends who support her in her badass adventures, or her enemies who she has to face off against. It could also include love interests, depending on the nature of the story.
It's Bella and Rosalie. Bella, the human - turned - vampire with a unique charm and a knack for getting into extraordinary circumstances. And Rosalie, the elegant and sometimes aloof vampire. As mates in this fanfiction, their relationship will drive the story. Their different backgrounds, Bella's human past and Rosalie's long vampire existence, will create interesting dynamics as they navigate their new relationship together.
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.
Obviously, Ash is one of the main characters. He's the one who experiences the betrayal and then transforms into a badass.
Another possibility is that there are characters from different timelines or dimensions because of the reincarnation concept. For example, he might meet versions of himself from other lives, or people who were important in his past existences. These characters would add more depth and complexity to the story, as Harry has to navigate his relationships with them while also dealing with his present - day situation in the wizarding world.
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.
I'm not sure specifically as there could be many different 'bella the badass fanfiction' stories. It might be about a character named Bella who is portrayed as a badass, perhaps she has extraordinary fighting skills, a tough attitude, and gets involved in all sorts of exciting adventures in the world created by the fanfiction writer.
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.
Issei is the central figure in 'badass issei fanfic'. But there are other characters too. For example, the villains he faces. They are designed to test his new - found badass skills. And then there are his comrades from his group who interact with him in different ways, depending on how his badass personality affects the group dynamics.
Well, popularity can be measured in different ways. If it has a unique take on Bella being a badass werewolf, it might attract readers who are tired of the more common portrayals. But it also needs good writing, engaging plotlines, and promotion within the fanfiction world to be truly popular.