Under the Act on Special Cases Concerning the Settlement of Traffic Accidents, Article 3 (Special Cases of Punishment), paragraph 2, proviso item 3, by how much must the speed limit be exceeded?

Answer: ① 20 km/h

Exceeding the speed limit by more than 20 km/h is one of the exceptions in which a driver who injures someone can be criminally prosecuted even with insurance or the victim's forgiveness. [Act on Special Cases Concerning the Settlement of Traffic Accidents, Art. 3(2)(3)]