Superman (1939) #237
"The Enemy of Earth" is written by Denny O'Neil with art by Curt Swan and Murphy Anderson. Superman has such a wide array of incredible powers and is virtually impervious to pain so, in practical reality, the only way to script a challenge great enough for the Man of Steel is to make it as complex as possible. In this tale, the Last Son of Krypton must use all of his powers, skills and intelligence to solve a spate of rapid-fire crises that barely give him a moment to catch his super-breath!
Witness Superman dealing with a crashing experimental rocket plane, a deadly space virus, a strange sand-like doppelganger of himself that robs him of his life-force, Lois Lane stranded in the jungle after a plane crash, flesh-eating army ants, a gang of bloodthirsty South American bandits, and giant insects. And if that weren't enough, Superman becomes convinced that he is carrying with him the keys to Earth's destruction. How can he save Lois or anyone else from fast-approaching danger when his very presence in the planet's atmosphere could doom the entire human race?