In Greek Mythology the King of the Gods is Zeus, God of the Sky
in Roman Mythology the King of the Gods is the same, but it is his Counterpart Jupiter, God of the Sky
In Egyptian Mythology, however, The first King of the Gods is Ra, God of the Sun until he gets replaced by Osiris Lord of the Dead as a result of Isis's scheming. Once Set kills Osiris and he becomes an "undead" God on account that he's not completely alive but not completely dead but becomes the God of the Underworld/ Duat. His son Horus becomes Pharoah, Which is the Egyptian version of a King.