The Galaxy Crimeteers
The Galaxy Crimeteers are a gang of murderous space aliens (Kill Kid, Murder Man, Oral) who send one of their own to Earth to destroy Superman using Kryptonite, and succeed in actually causing him to lose life signs. A sympathethizing android duplicate of the Man of Tomorrow made by the Crimeteers to practice their methods comes to Superman's aid at the cost of its own existence and Superman is able to apprehend the Galaxy Crimeteers with the help of an alien justice organization called the Peace Vigilantes (S No. 188, Jul 1966: "The School for Superman Assassins!").