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.
There could be a moment where Percy stands up to an unjust authority figure in the fanfiction world. He defies them with such confidence and charisma that it makes him seem like a total badass. Or perhaps he dives into a dangerous, unknown realm to save someone, showing his fearless and selfless side which is very badass.
One possible badass moment could be when bella stands up to a powerful alpha wolf. She shows no fear and uses her sharp tongue to put the wolf in its place.
One badass moment could be when Ezra single - handedly takes on a group of stormtroopers in a narrow corridor. Using his lightsaber and the Force to deflect blaster bolts back at them, he cuts through their ranks like a hot knife through butter. Another might be when he uses his Force powers to manipulate a large ship's controls from a distance to prevent it from crashing into a rebel base.
Dazai is not based on a true story. Usually, characters like Dazai are formed through the author's imagination and artistic expression to create an engaging narrative for the readers.