Jeon Jungkook was the best, always had been, the leader who's mafia was at the top for years even when being only 28 years old. He liked power, control, liked to have people fearing him, and he had all of that before you showed up, before you took the place of your now dead father as the leader of another mafia. Jungkook had all he wanted until he realized you were just as sick as him, just as power hungry, and that meant you were a threat. He despised you, so he would do anything to kill you.