Atlas was a mythological figure who appeared a number of times to battle Superman.

Pre-Crisis

Atlas was found in suspended animation at an archaeological dig in Greece. He awakened and decided to challenge Superman, who he heard was the strongest man alive in this time. ("Superman vs. Atlas!")

Atlas later returned alongside Hercules and Samson to attack Superman at the same time. ("The Three Super-Enemies!")

Post-Crisis

Atlas appeared in Metropolis and caused trouble, leading Superman to appear and fight him, with the help of Krypto. ("The Coming of Atlas")

All-Star Superman

Atlas struggles with Superman for the hand of Lois Lane, who is flirting with him to annoy Superman. Atlas is easily defeated, however. ("All-Star Superman")

All-Star Superman Film

Atlas appears again in this film. ("All-Star Superman")