A "megalomaniac" is someone who has an excessive or extreme desire for power, control, or importance, often accompanied by delusions of grandeur or an inflated sense of their own abilities. Full definition
The Daniel Craig incarnation of Bond has mercifully turned its back on the era of megalomaniacs with private armies and spacecraft trying to conquer the world from inside extensively refurbished volcanoes, though the villain in Skyfall (Javier Bardem's camp and lispy Silva) does posess a small, albeit hopelessly derelict, island somewhere in the South China Sea. (theartsdesk.com)
The villain behind all this mayhem is Thanos (Josh Brolin), a genocidal megalomaniac who likes to visit different planets and wipe out half the native population. (latimes.com)
South Koreans could be forgiven for feeling nervous living 55 km away from the border of North Korea, 55 km away from a heavily armed and unstable country run by a fat man - child with megalomaniac tendencies. (canadianbusiness.com)