Godawful Comics (NWS)

Superboy-Prime basically got his start in Crisis on Infinite Earths as a more faithful version of Superboy, from a universe where there weren't any other superheroes. The Anti-Monitor destroyed his home dimension, and at the end he, Lois and Clark from Earth-2, and a good-guy version of Luthor from Earth-3, went off to a sort of limbo because they didn't really fit into the Post-Crisis unified Earth (it already had a Superman, Lois, and Luthor after all)

Then after about twenty years, in Infinite Crisis, they come back. Earth-2 Lois dies of old age. "Good guy" Luthor reverts to the usual Luthor form and becomes a megalomaniac determined to reshape the universe to his liking. Superboy-Prime eagarly served Luthor-3 in hopes of getting his world back, and proves to be falling further and further away from the Superman tree by gleefully killing Conner Kent (the Post-Crisis Superboy) and a bunch of fourth-string characters from the Titans books. He whines the whole time about how it's their own fault for getting killed, too. He's imprisoned by the Guardians of the Universe after a titanic battle that leads to the heroic death of the Earth-2 Superman.

He is freed by the Sinestro Corp in the "Sinestro Corp War" storyline, then bounces around the Multiverse for awhile in Countdown, and in Final Crisis: Legion of Three Worlds he turns up in the 31st Century and teams up with Mordru, Absorbancy Boy Earth-Man, and the Legion of Supervillians, and goes on another killing spree, taking out the "Threeboot" versions of Element Lad and Sun Boy. Conner Kent is revived by the Legion (So is Bart Allen). They defeat Prime again, and reveal that the "Threeboot" Legion is actually native to Earth-Prime, which was restored by Infinite Crisis after all. Depowered, Prime is sent back to Earth-Prime in 2009, but his family hates him now because they read all the comics and know what he's done.

But it ain't over yet--he's slated to pop up again in Adventure Comics #4(507)