One great book with badass fictional characters is 'The Lord of the Rings' by J.R.R. Tolkien. Characters like Aragorn are badass. He's a skilled warrior, a natural leader, and has the courage to face the dark forces of Sauron. Another is 'Harry Potter' series by J.K. Rowling. Harry himself is a badass as he battles the powerful and evil Voldemort throughout his life at Hogwarts and beyond, not to mention his friends Hermione and Ron who are also very brave. Then there's 'The Hunger Games' by Suzanne Collins. Katniss Everdeen is extremely badass. She volunteers for the Hunger Games to save her sister and shows remarkable survival skills and defiance against the Capitol.
You should check out 'The Dark Tower' series by Stephen King. Roland is a badass gunslinger on a quest to reach the Dark Tower. He faces numerous challenges and enemies along the way, and his skills with his guns and his unwavering determination are really impressive. 'Ender's Game' by Orson Scott Card also has a badass character in Ender. He's a child prodigy who is trained to fight against an alien race. He has to endure a lot of psychological pressure and still manages to outwit his enemies.
One common theme is the idea of sacrifice. The badass warrior often has to sacrifice something for the person they love. For example, in 'Akame ga Kill!', Tatsumi sacrifices his own safety and well - being for Akame and their comrades. Another theme is growth. The love story often forces the warrior to grow as a person. In 'Rurouni Kenshin', Kenshin grows and changes because of his relationship with Kaoru. He becomes more open and less isolated.
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.
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.
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 could be characters like Draco Malfoy. In the original series, he had his moments of growth and in fanfics, he might be one of the main Slytherins to defend Hogwarts. Maybe he finally realizes the importance of the school and his own values change. He could be joined by other Slytherins who were perhaps overlooked in the official story but show their true courage in the fanfic.
One great anime is 'Akame ga Kill!'. It features a group of badass warriors fighting against a corrupt empire. Tatsumi, one of the main characters, has a complex relationship with Akame, which includes elements of love. Their story is filled with action, sacrifice, and a touch of romance.
Well, Akko is obviously the main character in 'badass Akko fanfic'. But often, her friends like Lotte and Sucy also play important roles. They might support Akko in her badass adventures, or sometimes they even get into trouble that Akko has to bail them out of.