Collects Crisis on Infinite Earths (1985) #1-12.
This is the story that changed the DC Universe forever. A mysterious being known as the Anti-Monitor has begun a crusade across time to bring about the end of all existence. As alternate earths are systematically destroyed, the Monitor quickly assembles a team of super-heroes from across time and space to battle his counterpart and stop the destruction. DC's greatest heroes including Superman, Batman, Wonder Woman, Green Lantern, and Aquaman, assemble to stop the menace, but as they watch both the Flash and Supergirl die in battle, they begin to wonder if even all of the heroes in the world can stop this destructive force..