megalomaniac

1882 (n.), "one suffering from megalomania;" 1883 (adj.) "afflicted with megalomania," from megalomania (q.v.).

The megalomaniac differs from the narcissist by the fact that he wishes to be powerful rather than charming, and seeks to be feared rather than loved. To this type belong many lunatics and most of the great men of history. [Bertrand Russell, "The Conquest of Happiness"]