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the ruler has seized his power by force
You just described most of the ancient world.
A tyrant in Ancient Greece means a ruler who had seized power without legal right to it. Today it means any person who exercises power in a cruel way.
Such a person is called a Dictator or a Authoritarian ruler
dictatorship
The kings, then the Tyrants. See the list Greek Tyrants in the separate panel Sources and related links: below.
Tyrant
Zeus was the ruler of the Greek Gods and Kronos was the ruler of the Titans.
If you mean 'dethrone'. It means to remove, usually by force, a ruler from power.
After the French Revolution and the ensuing bloodbath and chaos, a strong ruler was needed.
Zeus was often associated with the emotions of anger, power, and authority. As the king of the gods in Greek mythology, he was known for his fierce temper and displays of force when challenged.
Catherine The Great