Action Comics (1938) #1079

PRISON BREAK! 

In a last-ditch attempt to save both the Earth and the Phantom Zone from certain annihilation, Superman has been knocked for a loop and is only just now regaining consciousness. But what's that in the distance? The tiny silhouettes of every single Phantom Zone prisoner freed and heading straight for him? Uh oh... Plus, the true villain behind Supergirl's mission reveals himself!