I know here in Korea laws were passed a number of years ago to stop any kind of corporal punishment. I've personally seen corporal punishment and outright abuse happen in the past here. When I worked in a hagwon (this was back in 2004), one of my coworkers was quizzing an elementary school student on some work and when the student didn't get the answer correct, the teacher would hit the student on the hand with a ruler. A few years later while working at an elementary school I saw a male teacher who was outright abusive toward a student. The student was being disruptive and I asked him to stand outside the room hoping he'd come back and behave. He got worse and the homeroom teacher came down and I can't remember why but he was rolling on the ground and the teacher acted like he was going to stomp on the student.
In both situations I didn't say anything. Foreign teachers here are treated differently from regular teachers so the amount of authority we have over situations like these is somewhere around zero.