KAI KF-X was the model that followed which South Korean supersonic trainers and combat aircraft?
KAI KF-X:  It is South Korea's second fighter development program following the FA-50. KAI T-50 Golden Eagle: The KAI T-50 Golden Eagle (골든이글) is a family of South Korean supersonic advanced trainers and light combat aircraft, developed by Korea Aerospace Industries (KAI) with Lockheed Martin.
KAI T-50 Golden Eagle