Today's new edition to the roster of Badass Women in Anime is the devilishly beautiful and dnagerous woman responsible for Ichigo's early training days, and (maybe) partner to Urahara Kisuke:
Yoruichi is a 100% confirmed badass. Though she definitely still has silliness in her.
Yoruichi is so powerful that she only ever uses hand-to-hand combat as her fighting style. She never uses a zanpakuto. Her hand-to-hand is so amazing that she can perform Shunko, a bonding of hand-to-hand and kido.
Her mastery of shunpo allows her to move almost faster than is possible to percieve. With this, she is incredibly effective in dispatching her opponents.
She didn't even back down from taking on Aizen when he was reaching the height of his power. The height of all power, really.
For these reasons, (and many many more) Yoruichi is an undeniable badass.