From Longman Dictionary of Contemporary Englishegomaniace‧go‧ma‧ni‧ac /ˌiːɡəʊˈmeɪniæk, ˌeɡ- $ -ɡoʊ-/ noun [countable] SELFISHsomeone who thinks that they are very important, and does not care whether they upset other people in order to get what they want
Examples from the Corpus
egomaniac• Like a lot of people who are very good at what they do, he is an egomaniac.• Only an egomaniac would propose a Napoleonic construction effort as a plan for a city with fundamental social and economic problems. 