His first appearance was in the Showa series. Ghidorah was quite a threat and was barely defeated by mothra, Rodan, and Godzilla. The next movie Alien's tricked earth to release Rodan and Godzilla on their planet in zero gravity to battle King Ghidorah only to get mind controlled. The aliens released the monsters upon earth to wreak havoc. The two monsters broke free of their mind control and then fought Ghidorah once more. Many movies later he appeared in Godzilla vs Gigan and teamed up with the chicken-like creature named Gigan against Godzilla and Anguirus.
King Ghidorah was a group of small creatures called do dorats mutated by time travelers to wreak havoc against Japan. Godzilla is there to save the day but was nearly killed until the time travelers flying base knocked ghidorah down. Godzilla ripped two of King Ghidorah's heads off. Later he was revived into a Cyborg to have a final fight with in the city. In a later Heisei movie, King Ghidorah was battling a form of Mothra Leo.
King Ghidorah appeared as a guardian of the earth along with Baragon and Mothra against an evil Godzilla. After the trio of heroes were defeated, their spirits finished the fight, nearly killing Godzilla.
Ghidorah in the king of the monsters can survive massive explosions and regenerate its head and body.
More information will be coming soon on the king of the monsters.