Bobby Priest — a series by Jim Priest
Part of the Jim Priest universe

Bobby wrestles his younger sister, Jackie, and finds himself no match for her strong gymnast muscles and wrestling skills as she dominates him and causes conflicting feelings inside him which she exploits. Later at school she dominates him again in front of the whole school.

School bully Kevin gets a humiliating beatdown by a younger smaller oriental girl in front of the whole school

Girl Guides demonstrate the power of their merit badges to a smug bully

Bobby is outmuscled by his younger gymnast sister & foolish enough to box her

Ling Chan kick-boxing schoolgirl gives grown fighters a shock beating