During this Taekwondo match, this kid winds up and performs a round house kick to his opponent. His opponent falls to the floor, and when he tries to get up, he's too disoriented to keep fighting.

On the mat, the No. 2 fighter in the world in his weight class sheds his lighthearted nature to embody an intense attacker. “He becomes this other person in the ring,” his mother says. C.J. Nickolas ...