From Longman Dictionary of Contemporary Englishmegalomaniacmeg‧a‧lo‧ma‧ni‧ac /ˌmeɡələʊˈmeɪniæk $ -loʊ-/ noun [countable] MICONTROLsomeone who wants to have a lot of power for themselves and enjoys having control over other people’s lives —megalomaniac adjective
Examples from the Corpus
megalomaniac• If housewives can't get the help, how do megalomaniacs manage?• Wherever 007 goes, he can be sure of encountering megalomaniacs set on world domination.• Domingo, however, is no power-gobbling megalomaniac.• Just one of those casual I-can-do-anything-I-want-any-time-I-want-and-make-you-like-it gestures so beloved of megalomaniacs, mass murderers and the Gunmint.• Twenty-five years ago he was enthroned as the guru of the avant-garde; today he is isolated, some would say megalomaniac.• Similar megalomaniac schemes were proposed in the 1960s, but were never carried through.• Do you think I would have let the Master grow into the twisted megalomaniac he is if I could have prevented it? 