These words suggest repressive rule by a single person or group. Despotic is the clearest of these words in its disapproving indication of repressiveness and unrestrained power. Once this was not always true as the phrase benevolent despotism indicates. Now it more uniformly suggests a harsh and cruel wielding of power: despotic parents; a despotic leader. Dictatorial refers more neutrally to unrestrained power, usually in the hands of a single person, and can apply whether this power is used fairly or harshly: a dictatorial régime that took over from the corrupt democracy that preceded it. The word does, of course, often carry the same disapproval as despotic and can imply the same harshness of rule: the reign of terror during Stalin’s dictatorial leadership of the Soviet Union.

Tyrannical can suggest the arbitrary and abusive exercise of power concentrated in the hands of a single person; it is now less used to refer to government than to any mishandling of authority: a tyrannical office manager; a tyrannical union leader. Tyrannous is less commonly used than tyrannical, except for rhetorical flourish; it might refer to a whole situation rather than to a person: tyrannous laws.

Autocratic is the most neutral of these words, indicating one-person rule and referring descriptively to such a person’s absolute power rather than to how he exercises it: an autocratic father. Context can, of course, give the word a disapproving flavour: an arrogant and autocratic chief secretary.