in the 1600s the adverb "bad" went from meaning "incorrect" to being an intensifier - "they wanted that badly" (meaning he wanted it very much, as opposed to his want being poorly formed).

This form of hyperbole has extended over the years and orphaned to a point where now the [they wanted that] part is inferred and we can refer to something as "badass" or "baddie", understanding subconsciously that is implied that it's an extender of wanting/liking something "a lot" ("badly").