Cercyon

Cercyon was the king of Eleusis. He was well known for his cruelty to his daughter, who he buried alive when he realized she had child with his father, Poseidon. After that, she was transformed into a stream, Alope. He was also known to wrestle people for the throne, but since he was better, he was able to kill them. He was killed by Theseus.

Percy Jackson's Greek Heroes
In Percy Jackson's Greek Heroes, He is described as an insane man who terrified the locals and destroyed temples, and rampaging around in gold spandex pants. Apparently, he was as clumsy as a sow, so he was killed easily by Theseus. After his death, Theseus refused the throne and asked the town who was the smartest person in town, and they hesitantly pointed to an old man, supposedly Hippothoon, his grandson.