There are twelve main literary archetypes derived from Swiss psychiatrist Carl Jung's findings. The Ruler is one of the twelve:
The Ruler as a character archetype would be the one constantly exercising his/her/their power over the other characters, while also demonstrating the character's insecurity and worries ceaselessly about losing power and control over people/ place. The Ruler archetypes, therefore, will often be seen manipulating other characters while struggling to stay in power.
A fitting example of this character archetype would be the titular character Richard III from Shakespeare's history plays. Richard III is jealous, ruthless and overambitious. He becomes the King of England by means of deceit and manipulation. But once on the throne, the tyrannical usurper continues to feel insecure and proceeds to eliminate anyone he perceives as a threat to his position as the King, including his very own, one by one, until he gets killed on the Battle of Bosworth Field when he is unhorsed and calls for:
A horse! a horse! my kingdom for a horse!
But gets killed by the Earl of Richmond, Henry Tudor, who then claims the throne as Henry VII.