The Thing
The name bestowed, for want of a better one, on "a shapeless protoplasm" capable of assuming any form it pleases and of duplicating, do to the most minute detail, the characteristics of whatever being it has choosen to impersonate--which arrives in the twentieth century in February 1954, after having been banished from its own era--the year 40,000 A.D.--by a populace that had grown afraid of it. Temporarily stranded in the twentieth century, "The Thing" takes on the from of various individuals--including Superman--as part of its elaborate scheme to steal the advanced technological compontents necessary for the construction of a "time machine," with which is intends to return to its own era and set up a dictatorship. Superman ultimately destroys the creature, however, by luring it into the midst of a hydrogen-bomb explosion. "Whew! That H-bomb gave me a slight headache!" muses Superman. "But it finished my rival--completely! He couldn't adapt himself to an explosion of such magnitude!" (S No. 87/1: "The Thing from 40,000 A.D.!").
Superman teams-up with the Omega Men to face The Thing again in January 1986 (DCCP No. 89/1: "Metropolis Wasn't Built in a Day... or Was It?")