In The Mummy (1999): If Imhotep had defeated O'Connel, he would have killed Evie and fully resurrected his lover. Tragic, but hardly a catastrophe.

So what next? Does he conquer the world? Does he destroy it? Just how ambitious is he, and how evil? 

He has some sort of zombiefied followers, and the medjai warned that he was 'a bringer of death', but are vague.

Would it have been really so terrible for humanity if he had prevailed?