Kruge was a ruthless Klingon commander who tried to seize the secret of the Genesis device and died fighting James T. Kirk on the Genesis planet.
Kruge commanded a Klingon Bird-of-Prey in 2285. After learning about the Genesis device, which could transform a lifeless world, he saw it as an unstoppable weapon and set out to obtain it for himself. He killed his own informant to keep the knowledge secret and headed for the Genesis planet.
At Genesis, Kruge's forces destroyed the science vessel Grissom and captured Saavik, David Marcus and the revived young Spock. When Kirk arrived in the stolen Enterprise, Kruge threatened the prisoners to force him to give up the ship, and David was killed defending Saavik. Kirk pretended to surrender, then set the Enterprise to self-destruct, killing the Klingon boarding party. Kirk and Kruge fought hand to hand as the unstable planet tore itself apart, and Kirk finally kicked Kruge off a cliff into a fiery chasm. Kirk and his friends then took over Kruge's Bird-of-Prey.
Kruge was the main villain of Star Trek III: The Search for Spock, and his actions cost Kirk both his son and the original Enterprise.