It's sad that John Byrne's run on the Superman titles had to end like this, but it certainly was a well-crafted story to end that run on. Superman revisiting the Pocket Universe that Superboy came from, only to find that disaster befell it when its Lex Luthor accidentally let loose the three Phantom Zone criminals, and then having to deal with those criminals himself in a way that, although humane in a sense, marked him forever as having violated his Thou Must Not Kill ethic, was such a shocking swerve, it really made the Superman comics that much darker in tone than in the Silver Age/Bronze Age era, where such a thing would be relegated to an imaginary story like Whatever Happened To The Man Of Tomorrow.
One of the saddest Superman stories
It's sad that John Byrne's run on the Superman titles had to end like this, but it certainly was a well-crafted story to end that run on. Superman revisiting the Pocket Universe that Superboy came from, only to find that disaster befell it when its Lex Luthor accidentally let loose the three Phantom Zone criminals, and then having to deal with those criminals himself in a way that, although humane in a sense, marked him forever as having violated his Thou Must Not Kill ethic, was such a shocking swerve, it really made the Superman comics that much darker in tone than in the Silver Age/Bronze Age era, where such a thing would be relegated to an imaginary story like Whatever Happened To The Man Of Tomorrow.