Kronos

Kronos was the former ruler of Greece before he was overthrown by his son Zeus. Kronos is one of the Titans. He was first mentioned in the Hercules animated series episode "Hercules and the Drama Festival". It is implied that Kronos favored Hades. It is also implied that Kronos is the reason why Hades is evil.

Background
Kronos preceded his son Zeus as ruler of the gods. After he found out one of his newborn children would overthrow him, he began swallowing them one by one ― except for Zeus, who managed to escape thanks to his mother who instead tricked Kronos into eating a rock thinking it was Zeus. Later, Zeus returned and freed his brothers from his father's stomach, along with the rock Kronos swallowed. As an act of revenge, Kronos put a curse on the rock so that any God that comes near it will be placed in eternal sleep. He was then imprisoned in an unknown region of Tartarus.