despot
noun /ˈdespɒt/
  /ˈdespɑːt/
 - a leader with great power, especially one who uses it in a cruel way
- an enlightened despot (= one who tries to use his/her power in a good way)
 - It is the story of a military coup which brings a brutal despot to power.
 
Word Originmid 16th cent.: from French despote, via medieval Latin from Greek despotēs ‘master, absolute ruler’. Originally (after the Turkish conquest of Constantinople) the term denoted a minor Christian ruler under the Turkish empire. The current sense dates from the late 18th cent.