The 1980s were a complicated time for comic books. Not only were readers maturing, they expected the comic books they were reading to mature right along with them. Further, an ever-expanding mythology and a web of separate but interconnected realities was making DC Comics more complicated than almost any of their competition. This heralded the need for a change to the structure and intent of DC's line, and Superman was one of the most complicated and thinly spread characters of all.
During the course of Crisis on Infinite Earths, the event that DC designed to streamline its continuity, myriad alternate realities were destroyed and collapsed to form one core continuity. Among those worlds was Earth Prime, a reality with the distinction of being one of the most unnecessary and impressively misguided alternate realities of all. Earth Prime was essentially the real, non-comic book, mundane world, where no one had powers and people read Superman comic books.
When young Clark Kent, coincidentally named after his favorite hero, Superman, reaches maturity, he discovers that, woops, Earth Prime ain't so different after all, and that he is Superman. When Earth Prime is swept into the Crisis, Superboy Prime joins several other iterations of the Man of Steel in defeating the Anti-Monitor and saving the new reality, after which he and several of his friends, a job well done, are shunted off to a "Paradise Dimension" where loose threads never dangle, and there is no meta-plot.
Years later, after decades spent watching the universe he worked to save change and evolve time and time again, Superboy Prime gets so mad that he starts punching the walls of the Paradise Dimension, altering reality with his adolescent tantrums. Classic Superman stuff. When he and his companions finally break loose of the prison in which they willingly adjourned themselves, Superboy Prime goes on a rampage, joining the Anti-Monitor in un-altering reality, restoring the needlessly complex pre-Crisis status quo, and pretty much ruining everything for everyone.
In the process, Superboy Prime managed to kill a whole bunch of people, including Kon-El, the clone of his alternate reality self, effectively completely the craziest time-loop scenario outside of the whole Cable/Cyclops debacle, and solidifying his place as one of the most obnoxious villains of a whole era of DC Comics.