Imperiex Prime had detected imperfections in the fabric of the universe, and his ultimate plan was to destroy it and create a new, perfect one. To do so, in 2000, he headed for Earth, a planet which, according to his calculations, was in a position holding the universe together at that moment, in order to destroy it and therefore induce a new Big Bang. Before arriving to Earth, Imperiex obliterated countless other planets. Kalanor, Karna, and Daxam are three known planets destroyed in his cataclysmic campaign. Whole galaxies were also targeted for demolition as Imperiex Prime sought to fulfill his destructive destiny, obliterating one universe so that a new one would be born. He was opposed by many forces and, in his final moments, realized, in an ironic twist, that the imperfection he had detected in the universe was himself.
Note: Imperiex, being described as the embodiement of entropy, bears a huge likeness to the being described in the Marvel Universe as the Proemial God Diableri of Chaos . There goals are also the same.
Source: DC Universe, Superman #153, (February 2000), created by Jeph Loeb and Ian Churchill.