Rebelle, the French adaptation of Kaoru Matsubara, operates as the superhero Powered Buttercup. She gained her powers when a white Chemical Z ray struck her alongside two other middle school students. Her civilian life involves residing with her parents and two brothers, including a professional wrestler father. Athletic and competitive, she excels in soccer, tennis, and martial arts, with soccer prowess stemming from childhood determination after receiving new cleats. Her athletic skills attract fan attention, which she dislikes. Initially, she resents her teammates for their femininity and values her powers solely for the physical strength they provide. As a superhero, she wears an outfit with a skirt, finding it uncomfortable due to her aversion to girly clothing.

Powered Buttercup wields a giant mallet to generate shockwaves or energy blasts in combat. As her team's physically strongest member, she favors direct confrontations, employing punching combos and hammer strikes that reflect her aggressive, tomboyish nature. She retains the original Buttercup's catchphrase about saving the world "before bedtime," despite its questionable relevance to her age.

Her character evolves from hostility toward her teammates to mutual respect and cooperation, and she reluctantly mediates team conflicts. The Rowdyruff Boys, recurring adversaries created by Mojo Jojo using her DNA and her teammates', are biologically related to her in this adaptation. Balancing superhero duties with school causes academic struggles. Her teacher, Miss Keane, remains unaware of her secret identity, and repeated mission absences require extra tutoring to maintain grades. She attends these sessions reluctantly but commits to self-improvement.

Beneath her tough exterior, she exhibits kindness and humor, particularly outside combat. Her design includes dark gray hair with green clips, green eyes, and a green superhero costume with star motifs. Early episodes depict a lean build, while later ones suggest subtle maturation.