The Day of the Krypton Man concludes in Action 652 (April 1990), by Stern, Perez, Gammil and Breeding.
Ma and Pa Kent have become distressed at Clark’s behaviour, which they have seen on television, when he battled and almost killed Dragga. They come to Metropolis, and find their son has become completely Kryptonian.
He brings them to his Fortress of Solitude, built by the Eradicator as a celebration of his heritage. Superman spends much of the story arguing the superiority of emotionless logic.
But when the Eradicator uses the Fortress to attack the Kents, Clark’s emotions take control, and he gets a grip on himself, realizing how much he has been altered by the Eradicator.
Superman destroys the Fortress, bringing it down on the Eradicator, which he then throws into the sun.
Like tossing something Kryptonian into an empowering yellow sun would destroy it.