Adventures of Superman #504 (1993)

Superman, Superboy, and Man of Steel arrive outside Engine City, where Cyborg Superman sees the three heroes approaching and is now starting to wonder who the one in the black suit is. Mongul taunts Cyborg by saying that it could be his enemy Superman come back from the dead, but Cyborg twists Mongul's arm to remind him who holds his leash. The three are soon greeted by laser fire. They charge straight toward the city and break in, instantly dealing with the goons sent to run as interference. After taking them out, Superman grabs some of their weapons and arms himself with them, realizing that his power levels aren't back to normal and that he needs all the help he can get. They now fight their way into a launch chamber, where they see a massive rocket armed and ready to turn Metropolis into "Engine City, Part Deux". Again they run into thugs, but that is the least of their problems; Cyborg Superman now orders a launch, which means they need to escape or else get fried in the rocket's exhaust flares. Superman and Man of Steel (whom is now called Steel) manage to find cover, but Superboy ends up riding the rocket in an attempt to stop it. Superman realizes that and decides to press on in his journey, making a daring jump into the launch chamber after the rocket has departed while Steel watches in amazement. Lex Luthor, the Daily Planet staff, Tana Moon, and even the citizens of Metropolis watch as Superboy exerts all his strength and willpower into diverting the rocket's trajectory. Suddenly the rocket barely scrapes past the Daily Planet globe on top of the building as it rises high into the air, where it detonates, causing Tana to break into tears as she realizes that Superboy may be no more.