King Patrick is one of Patrick Star's alter egos. He believed that being a king meant he could do whatever he wanted. King Patrick is known to be cold-hearted and selfish, doing cruel things such as:
Stealing comic books from nerds that have spent their entire lives collecting them
Forcing people to give him all of their stuff
Forcing people into being essentially slaves to him with undying loyalty to him
In "Rule of Dumb" (his only appearance), he abuses his power and he stays like this until he sees a monstrous version of himself in the mirror. This makes him change his attitude, and become his old self again. Mr. Krabs and Squidward were the only ones who stood up to him.