SUPER SOLDIER!!! Marvel and DC co-produced a line of comics where their two universes collide and become one after the Spectre and the Living Tribunal combines the two universes in order to save their very existences from powerful cosmis beings called the Brothers. When Clark Kent takes a super soldier serum that contains alien DNA retrieved from the remains of a dead alien, he becomes… the Super Soldier. He is now as powerful as Superman with the spirit of Steve Rogers and an S symbol shield. After defeating the Ultra-Metallo, the two sink into the icy northern waters. Clark is discovered in the ice and brought back to the world as part of the JLA, the Judgement League Avengers. After the Brothers are defeated, the universes go back to the way they were before with no one having any memory of the Amalgam universe. 

First appearance Marvel vs DC #3 April 1996. Created by Ron Marz and Dan Jurgens.