Ghidorah, the Three-Headed Monster (1964): The original version of the monster is an alien who travels to Earth in a magnetic meteorite, and devastates Japan until repelled by Godzilla, Rodan, and Mothra.
Invasion of the Astro-Monster (1965): Ghidorah is now the mind-controlled pawn of aliens from "Planet X", and refer to Ghidorah as "Monster Zero". The "Xians" covet Earth's water resources and also take control of Godzilla and Rodan in an attempt to conquer the planet. When Earth forces free Godzilla and Rodan, the pair drive Ghidorah off into space.
Destroy All Monsters (1968): Set in the future, Ghidorah is controlled by the alien Kilaaks. The monster is eventually killed by Godzilla and several other monsters.
Godzilla vs. Gigan (1972): Set in the present day, Ghidorah teams with fellow monster Gigan until both are driven away by Godzilla and Anguirus.
Godzilla vs. King Ghidorah (1991): Time-travelers from the 23rd century (called "Futurians") travel to the past to release three genetically-engineered bat-like creatures called "Dorats" at the location at which a Godzillasaurus was to be exposed to radiation and become Godzilla. The irradiated Dorats fuse into King Ghidorah, which the Futurians then use to devastate present-day Japan. Godzilla eventually battles and cripples Ghidorah, with the wounded monster falling into the ocean. The Futurians, however, locate Ghidorah in the future, and using advanced technology create the cyborg "Mecha-King Ghidorah". The monster battles Godzilla to a standstill, before both disappear into the ocean.
Godzilla, Mothra and King Ghidorah: Giant Monsters All-Out Attack (2001): Godzilla again attacks Japan and is repelled by the combined might of the world guardian monsters (Baragon, Mothra, and Ghidorah) and the Japan Self-Defense Forces.
Godzilla: Final Wars (2004): Godzilla defeats every monster ever encountered before battling "Monster X", a disguise for a version of "Keizer Ghidorah".
The monster also featured in two films in the Mothra trilogy, both of which involved time-travel and different versions of Ghidorah:
Rebirth of Mothra (1996): A version of Ghidorah, referred to as "Desghidorah" (or Death Ghidorah) appeared as a black, quadrupedal, three-headed extraterrestrial dragon. Freed from imprisonment in a prehistoric cave, the creature battles both an adult and larvae form of Mothra before being entombed once again.
Rebirth of Mothra III (1998): Ghidorah appears in a more traditional form known as "Grand King Ghidorah" and battles Mothra Leo, who undergoes several transformations to match the monster.
King Ghidorah has had a number of changes made to himself over the years, but most of his traditional battle characteristics have remained the same. His different forms in the different movies have their own abilities.
King Ghidorah flies at the speed of Mach 3, is able to fire Lightning Beams, which are called Gravity beams, from his mouths, is able to create hurricane winds from his wings, and uses his necks to constrict an opponent.
Mecha-King Ghidorah (メカキングギドラ, Meka Kingu Gidora) is a mechanically modified Ghidorah that appeared in the 1991 film Godzilla vs. King Ghidorah. He has a futuristic and mechanical look, with his middle head mechanized as well as his wings, torso and a few other areas. He's considerably more powerful than the purely organic King Ghidorah.
Godzilla vs. King Ghidorah
Upon defeating King Ghidorah and sending the brass behemoth to his doom in the depths of the sea, Godzilla began to wreck havoc throughout Japan. Emmy Kano, a Futurian who rebelled against her belligerent crew, was asked if King Ghidorah could be revived in the 23rd century. If possible, he could be brought back to the present and used as an anti-Godzilla weapon to protect Japan. Emmy agreed with this request and ventured into the future using the time machine KIDS.
As Godzilla continued his rampage through the center of Tokyo, he suddenly heard a sound in the sky. King Ghidorah, now the cyborg Mecha-King Ghidorah, materialized in a flash of pulsing energy. Piloted by Emmy and reinforced with several robotic segments, Mecha-King Ghidorah easily outclassed his predecessor. He fired his gravity beams and triple laser beam at his foe. Though Godzilla managed to fire his thermonuclear breath in retaliation, the gray gargantuan was ultimately sent crashing into the surrounding buildings. Godzilla managed to regain his balance and damage both of Mecha-King Ghidorah's wings. It was time for Emmy to reveal the cyclopean cyborg's most powerful technique. Energy-conducting capture cables were fired, as was the machine hand restraint. Mecha-King Ghidorah lifted Godzilla into the sky and over the sea, but both were sent crashing into the waves when Godzilla fired his thermonuclear ray at his captor. Emmy quickly escaped in KIDS, leaving both monsters trapped on the ocean floor.
Meanwhile, beneath the surface of the sea, Godzilla's eyes glowed eerily. He released his thermonuclear ray into the azure abyss, for he would escape from its restraints and return to terrorize the world another day.
Godzilla vs. Mechagodzilla II and Godzilla vs. SpaceGodzilla
The technology used in Mecha-King Ghidorah was later used to create MechaGodzilla 2 and Moguera.