Buttercup is considered the best Powerpuff Girl because she is the toughest fighter among them. She defies traditional gender roles by not conforming to the stereotypical "girl" behavior. She loves getting dirty, fights with immense strength, and plays rough. Her uniqueness lies in her ability to curl her tongue, which adds to her distinctiveness and charm. With her fierce determination and powerful skills, Buttercup stands out as a fierce and independent character in the Powerpuff Girls series.