WordNet sense 1 (offensively self-assured or given to exercising usually unwarranted power):

bossy, magisterial, peremptory, dominating, high-and-mighty

WordNet sense 2 (tending to domineer):

domineering

WordNet sense 3 (characteristic of an absolute ruler or absolute rule; having absolute sovereignty):

authoritarian, despotic, dictatorial, tyrannical

WordNet sense 4 (not in agreement with or according to democratic doctrine or practice or ideals):

undemocratic