Imperiex is a massive and overwhelmingly powerful villain. His goal was to destroy the entire universe, and he came close to doing just that. All the heroes and many of the villains of the DC Universe had to come together to defeat him in Our Worlds at War. He was eventually consumed by Brainiac 13 and his Warworld, and the two were sent back to the beginning of time, where they were destroyed by the formation of the universe.
A different version of Imperiex appeared in the 31st century, where he became a main enemy of the Legion of Superheroes. This Imperiex was destroyed by Brainiac 5, who had reawakened his original Brainiac programming.