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.
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.
In some fanfictions, Snape has badass moments when he outsmarts Voldemort. For example, he manages to mislead Voldemort about the location of a crucial magical artifact. He uses his Occlumency skills to his advantage, hiding his true thoughts and intentions while presenting false information in a very clever way. This not only shows his intelligence but also his courage as he risks his life to deceive the Dark Lord.
His attitude. Percy in fanfiction often has a 'don't mess with me' attitude. He doesn't shy away from a fight and is always ready to stand up for what he believes in. He'll face any opponent, no matter how powerful, without hesitation.
His unwavering determination is another factor. No matter how tough the situation is, Adrien in fanfictions doesn't give up. He is willing to risk everything to protect the people he loves and the city he lives in. This strong will and selfless attitude are what make him a truly badass character in many fanfictions.
In 'badass ship girl fanfiction', one characteristic is the intense action. The ship girls are constantly engaged in battles, whether it's against other ship girls or some kind of sea - based monsters. Their badass nature is shown through their combat skills, strategic thinking, and their ability to make quick decisions in the heat of battle. Also, they usually have a sense of loyalty, either to their comrades or to a cause they believe in, which adds depth to their characters.
Rachel's talent also plays a big part. She's a great singer in the show, and in fanfiction, this talent is often magnified. She can use her voice to inspire others or to outshine her rivals, which gives her that badass aura. Also, her ability to overcome obstacles, such as dealing with mean comments from other characters, is emphasized more in fan - written stories.