Commander Kruge

Commander Kruge was the commanding officer of a Klingon Bird-of-Prey during the late 23rd century. He was also the lover of the Klingon spy Valkris and had a pet monster dog. 
In 2285, after receiving intelligence on the powerful Genesis Device from the freighter Merchantman, Kruge took his ship and crew to the Genesis Planet in a rogue operation aimed at stealing the technology, which he perceived as a weapon. Upon entering Genesis orbit, Kruge ordered a deadly attack on the Federation science vessel USS Grissom, killing the entire crew, save Genesis scientist David Marcus (James T. Kirk's son) and Lieutenant Saavik, who were on the Genesis Planet conducting a survey mission. His intent, however, was not to kill the crew; he only ordered their engines targeted, so that he could get information from them. He promptly executed the officer that made the "lucky shot". Later in the Genesis incident, he ordered the execution of one of the prisoners as "enemies of galactic peace". As the Klingon crewman moved to stab Saavik, Marcus stepped in to stop him and ended up being stabbed in the chest instead. This devastated Kirk beyond measure and would haunt him for years afterward. 
Kruge intended to seize control of the USS Enterprise following an attack on the Federation starship which left the vessel disabled. However, Admiral Kirk beamed his crew down to Genesis and lured Kruge's boarding party aboard the Enterprise with the auto destruct sequence armed. When Kruge's officers informed their captain of the mysterious countdown taking place on the bridge, Kruge tried to warn them off the ship, but it was too late and the Enterprise exploded, killing Kruge's men in the process. 
 
On the surface of the Genesis planet, Kruge tried to thwart Kirk's attempts to secure the body of Captain Spock and tried to bargain Spock's revived body for the Genesis technology. As the Genesis planet began to break up, Kruge battled Kirk in a lengthy fistfight, and was killed after Kirk kicked him into a sea of lava.
The following year, the Klingon Empire demanded that the Federation Council extradite Kirk to stand trial for the deaths of Kruge and most of his crew. The Council denied this request.