Word for someone who is hungry for power and control
Solution 1:
Such a person (as Darth Vader, not an ELU moderator! :) would be called a...
megalomaniac - a person who has an obsessive desire for power
The adjectival form megalomaniacal does occur, but it's nowhere near as common as the noun.
Solution 2:
power-hungry: what it says
control freak: someone who has a great desire or a compulsion to control things (including other people)
power-hungry control freak: 1 + 2