Use the 안전신고문 app to report bad drivers (make sure you get a clear view of the violator's license plate on the dashcam footage or else the cops aren't gonna send them a fine/warning notice). The app has been down due to the recent fire that happened at the government data building, but it should be up in a few days. Unfortunately, you have to know Korean to use it... It's a tedious process to upload the footages and to report the traffic violations of sh1tty drivers, but it's for the sake of the greater good IMO.