Triangle 1993-30.
Continued from Superman: The Man of Steel #26 and continues in Adventures of Superman (1987) #505.
Green Lantern, the Eradicator, and Superboy arrive at Engine City as Superman is being badly beaten by Mongul. Enraged by what has happened to his hometown, Green Lantern takes Mongul off Superman's hands so he can go after the Cyborg Superman.
Green Lantern and Mongul's fight continues in Green Lantern (1990) #46.
Steel, Superboy, and Supergirl are trapped by the cyborg's evil mechanizations, leaving the Eradicator and Superman alone to face the cyborg in battle. He reveals to Superman that he is in fact Hank Henshaw and has returned to get his vengeance upon the Man of Steel for forcing him to leave Earth. As a last resort Henshaw unleashes the power source of Engine City, pure Kryptonite, upon Superman but the Eracicator dives in front of him, determined to protect the sanctity of Kryptonian life.
This horrible blast of pure Kryptonite radiation, filtered through the newly recharged Eradicator, returns Superman's powers to him and he easily defeats the now weakened Cyborg Superman.