“Finish him!” That booming command in the 1992 video game “Mortal Kombat” meant one character had just defeated another in a martial arts bout. The victorious player could then press a series of buttons to execute a “Fatality” — a gruesome finishing move, such as ripping off a victim’s head while pulling out his spine or uppercutting a victim into a pit of spikes. Unlike other fighting video games of the time, punches and kicks in “Mortal Kombat” resulted …