Megalomaniacs are obsessed with the accumulation of power and wealth. They're arrogant and convinced of their own superiority. When they work towards achieving the status they "deserve" they can compose complex and devious conspiracies or use outright brutality.
To a megalomaniac the world has only two kinds of people; those who are weaker, and the undeserving. The undeserving are people in positions of power, but who do not deserve it.