Action Comics #751

In "Sixes and Sevens," Superman and Geo-Force race to prevent a catastrophic nuclear meltdown in Markovia, testing the limits of their strength and resolve. As Lex Luthor pushes forward with his artificial Green Kryptonite project, Superman faces new strain—both from a dangerous test of the synthetic kryptonite and from the relentless pressure of being everywhere at once. Written and illustrated by Stuart Immonen, with cover art by Immonen and José Marzán Jr., this 1999 issue captures Superman at a breaking point, grappling with the weight of his responsibilities.