Originally he believed the DC universe was a horrible place, and wanted to destroy it to bring back his on, more wholesome existence, if I remember correctly. I think he was being manipulated by an alternative universe Lex Luther. Regardless of the noble vein of his original intentions he quickly became little more than a card carrying villain, and a pretty poor one at that. He was always TOO powerful to generate a genuine threat. Joker has no powers, but is an effective villain because of his unpredictability. Lex Luther has no powers, is an effective villain because he genuinely believes he is in the right, and that sort of conviction is terrifying. Superboy Prime just reads like a teenager throwing a strop, and he is so powerful the reader knows that he never truly has any chance of achieving his goals. I mean if he did it would be the end of the DC universe.

Frankly Yog, I'd be happy to never see a Superboy Prime character in this RP, either PC, NPC or Antagonist.