A possible reason that the name "Destroyer" isn't commonly used in various markets is because the word itself could not be trademarked. It is referred to as "Destroyer" in the dubbed version of the film, while "Destoroyah" is Toho's official name for the character.
Destoroyah grows quickly and adopts several appearances throughout the film, including its micro form 3-mm, insect-sized, 2-meter, and 18-meter crab-like forms, a larger aggregate crab-like form, a bat-like flying form, and a bipedal 120-meter, demonic final form. Though Destoroyah may seem to be enormous, he is actually the same size as Moguera, SpaceGodzilla, Mechagodzilla 2, the millennium versions of Gigan and Hedorah, Monster X, and surprisingly Biollante.
Destoroyah first emerges as his small, crab-like form that ends up escaping from the possession of numerous scientists due to the careless actions of a security guard. He makes his way into an aquarium and kills many of the fish. He eventually escapes and grows into its 2-meter form, destroying a bridge and then hiding in a factory. The Japan Self-Defense Forces (JSDF) sends in numerable soldiers to attempt to destroy the creatures, but their assault rifles cause no damage to them, who badly wound and kill a number of JSDF. Eventually the JSDF attacks them with flamethrowers, badly wounding the aggregates and causing them to retreat. It becomes known that the aggregates are vulnerable to extreme heat or cold.
The JSDF deploy a squadron of Maser Tanks and missile batteries armed with Ultra Low Temperature lasers (ULT Lasers) and cooling shells. When the aggregates emerge again, they begin bombarding them with the freezing barrage. It seems to be working against the creatures, until they all converge on one position and merge into one giant monster. The giant aggregate then transforms into a giant bat-like form and flies away.
When trying to think of another way to defeat the destructive monster, the JSDF decides to try to lure Godzilla to Destoroyah. They reluctantly agree to the plan, despite protests from the psychic Miki Saegusa, and decide to lure Godzilla Junior to Destoroyah, knowing Godzilla will follow. Miki and another psychic fly out to Junior and use their psychic powers to make him change his course for Tokyo. When Junior arrives, Destoroyah attacks him in his flying form. Junior is battered by the stronger monster, until he manages a lucky shot and brings the flying form down. Destoroyah quickly recovers, attacking Junior in his giant aggregate form. Destoroyah pins Junior beneath his massive body and tears into his skin with his double jaw, injecting him with micro-oxygen. When all hope seems lost, Junior fires one last blast at Destoroyah, knocking him into the air. Junior then fires one final radioactive blast, sending Destoroyah flying and crashing into a factory.
When Godzilla finally arrives in Tokyo, the final form of Destoroyah rises from the fires of the factory. The vile behemoth takes to the air and flies toward Godzilla and his son, striking Godzilla to the ground and grabbing Junior in his massive claws. He flies high into the air and drops Junior, sending the young godzillasaur plummeting to the hard ground. Destoroyah then blasts Junior with its micro-oxygen beam, killing the young dinosaur.
After Godzilla fails to revitalize his fallen son, the grief in his heart causes his Nuclear meltdown to begin to go critical. The JSDF quickly dispatches the Super X-III and the maser tanks armed with freezing lasers to stop Godzilla's meltdown. As Godzilla continues to mourn his son and his nuclear heart begins to overheat, Destoroyah returns again. The evil beast strangles Godzilla with his tail and then throws Godzilla away from his son and prepares to battle again. Godzilla rises, and his dorsal fins and dorsal plates begin to melt and as the meltdown begins. The overload of power causes Godzilla's ray to increase in strength to immeasurable levels beyond infinity. Godzilla then unleashes his breath, increased in power by his meltdown, which blasts Destoroyah apart and decimates the landscape around it. As Godzilla begins to melt Destoroyah notices and being fatally wounded by Godzilla's Red Spiral Destruction Of Death Atomic Breath tries to escape from the meltdown by flying into the air to die elsewhere. However, the JSDF and Super X-III blast out its wings while it is distracted. Destoroyah then plummets towards Godzilla, and misses him just by a few meters. At this point, because of the extreme change in temperature from both the freeze weapons from the JSDF's attacks and the extreme heat from Godzilla's meltdown, Destoroyah explodes and evaporates into a cloud of micro-oxygen that quickly vanishes, killing him for good.
Destoroyah is considered by many to be Godzilla's ultimate foe, a title that is only shared by a handful of other monsters, such as King Ghidorah, Spacegodzilla, and Mechagodzilla. This is because Destoroyah could survive multiple hits from Godzilla's red spiral atomic breath, an attack which instantly killed most enemies in only one shot. Destoroyah also made Godzilla fight extremely harder than in any other movie, only when Godzilla was almost at his meltdown was Destroyah completely outmatched and fatally wounded. Destoroyah is quite possibly the most powerful evil monster ever created, and an exceptionally evil villain, having shown to enjoy killing other life forms. In fact, he is the only villain in the entire Godzilla franchise to succeed in killing Godzilla's son, a feat that many other Godzilla villains never attempted or achieved.
Like Hedorah, Destoroyah is a composite life form formed from trillions of near-microscopic organisms and thus possesses vast capacities to adapt and regenerate. The base organism resembles a miniature horseshoe crab barely larger than a speck of sand. Trillions of these creatures would later combine to form Destoroyah's aggregate form which manifested as several man-sized crustacean monsters which were reminiscent of the Alien. When threatened by the JSDF, the creatures merged again into a larger aggregate form and then into its winged bat-like form. After being wounded by Godzilla Junior, Destoroyah regenerated into its demonic ultimate form and would later temporarily separate into its aggregate form in an attempt to overwhelm Godzilla during their battle. It appears that when the individual Destoroyah organisms fuse, they all die if the resulting creature is killed before it can split up into a smaller form and reform, this is shown when Godzilla fatally wounds Destoroyah by blasting his exposed floral pattern on his chest and Destoroyah breaks up into a smaller form but when the Super X-III and Godzilla blasted out his wings the Super X-III used the ice laser and froze it at a microscopic level, he couldn't separate and thus all the Destoroyah organisms making up the final form were killed.
Destoroyah's primary weapon was a micro-oxygen ray fired from his mouth which could vaporize organic matter and was even capable of penetrating most metals. Despite this, Destroyah's micro oxygen spray wasn't able to dissolve Godzilla's hide. All of Destoroyah's forms possessed the ability to fire the ray but its aggregate form was also equipped with a pair of extending secondary jaws that injected the micro-oxygen directly into an opponent's bloodstream. In its final form, the horn projecting from Destoroyah's forehead had the ability to generate a blade of energy powerful enough to cut through even the strongest monster flesh. The aggregate forms were equipped with spiked claws similar to those of a praying mantis while Destroyah's flying and ultimate forms possessed a tail tipped with a grappling pincer that was strong enough to even hold Godzilla. It also has incredible physical strength befitting its monstrously huge size, able to drag Godzilla along the cold ground while flying. In the video game Godzilla: Save the Earth, Destoroyah has freezing breath for a special ability, which is ironic, because in his film appearance, he is vulnerable to ice.
The Oxygen Destroyer was a fictional weapon that appeared in the 1954 film Godzilla. It was an extremely powerful chemical compound that was able to completely dissolve Godzilla and wipe out all life in the Tokyo Bay. It was also the only weapon that was truly effective against the monster.
Unintentionally discovered by Daisuke Serizawa during his experiments, the Oxygen Destroyer dissolved oxygen in water which instantly reduced any and all organic life within range to its skeletal frame. While it's never explained how removing oxygen causes such a destructive reaction, since the laws regarding the conservation of mass state that matter and energy can't be destroyed but only converted into another form, it is possible that the Oxygen Destroyer actually converts oxygen into an entirely different element with highly corrosive properties. In the film, Serizawa was hesitant to use his discovery for fear of the damage it would cause and political implications therein, but ultimately relented when he realized Godzilla was the greater threat. But to prevent the formula from being perverted into a wholesale weapon of mass destruction he destroyed his research documents and subsequently took his own life.
In Godzilla vs. Destoroyah (1995), it is revealed that the Oxygen Destroyer awakened and mutated Precambrian life forms that lived in Tokyo Bay that would merge to form the strongest Kaiju ever recorded (taking Godzilla at the peak of his power, Godzilla Junior and Super X combined to finally destroy him) Destoroyah.
In the continuity of Godzilla, Mothra and King Ghidorah: Giant Monsters All-Out Attack (2001), it is disclosed that the use of the Oxygen Destroyer in 1954 was never made public and the defeat of Godzilla had been officially credited to the Japan Self-Defense Forces. This was done to spare the then newly established Self-Defense Force from public scorn after its inability to defeat the monster militarily.
Stock footage from the first Godzilla film was also used in Godzilla Against Mechagodzilla (2002) and Godzilla: Tokyo S.O.S..