Anguirus

Anguirus is the secondary antagonist in the 1955 film Godzilla Raids Again and a supporting antagonist in the 2004 film Godzilla: Final Wars.

Godzilla Raids Again
Anguirus first encountered Godzilla in Godzilla Raids Again, on Iwato Island. The two ancient creatures fought then fell into the sea below and disappeared. After some research was carried out, Anguirus was revealed to be an ancient and incredibly strong dinosaur from the Cretaceous Period. The two kaiju resurfaced and met each other again in Osaka, Japan, where they fought. After a fierce and destructive battle, Godzilla gained the upper hand when he bit Anguirus in his neck then threw him into a moat near Osaka Castle, before finishing him off with his atomic breath.

Destroy all Monsters
In Destroy All Monsters, Anguirus was now living on Monsterland along with the other Earth monsters in the year 1999. The Earth was invaded by the Kilaaks, however, and he was sent to guard the aliens' earth base. The humans intervened, and freed the monsters from the alien mind control. Anguirus battled King Ghidorah once again, and managed to kill him with the other monsters.

Godzilla vs Gigan
Almost 30 years after the events of Godzilla Raids Again, in Godzilla vs. Gigan, a new Anguirus arrived, this time to save Japan. Godzilla and Anguirus were now living on Monster Island, and Godzilla sent him to Japan to check on a strange noise they were hearing. Anguirus swam to the shores of Japan, where he was attacked by the military. The military managed to drive him off, but he returned to Monster Island to inform Godzilla. Godzilla returned with him to Japan, where they fought Gigan and King Ghidorah at the World Children's land. They defeated the enemy monsters, but were very badly injured in the process.

Godzilla vs MechaGodzilla
Three years later, in Godzilla vs. MechaGodzilla, Anguirus, having been resting and travelling underground ever since he fell into the fissure a year earlier, travelled to Japan in search of Godzilla. Anguirus knew something wasn't right, when he saw his friend Godzilla was attacking buildings mindlessly and walking around the Japanese countryside with no specific pattern. Anguirus burrowed out of the ground after Godzilla attacked an apartment building, tripping him over. Anguirus then challenged Godzilla, but Godzilla threw him through a bridge and into a valley. As Anguirus got back up, he leapt out of the valley, knocking off some of Godzilla's scales with his claws as he passed, revealing metal underneath. The now-revealed Fake Godzilla then fought back viciously, beating Anguirus and slamming him into the ground. The Fake Godzilla broke Anguirus' jaw in a violent and bloody fashion, forcing Anguirus to burrow back underground and retreat. Chronologically, this wasn't Anguirus' last appearance in the Showa era, as at some point between 1975 and 1999, he was found and taken to Monsterland, his injuries having been completely healed.

Godzilla: Final Wars
In the year 2004, Anguirus was under the control of the Xiliens and was sent to attack Shanghai. He was attacked by the Karyu, but he proved too fast for it. He continued to fight against the humans, but he was recalled by the Xiliens on their commander's orders. Once X killed the commander and led the Xiliens himself, Anguirus was brought back to Shanghai, and destroyed the Karyu after slamming into it after curling up. After Godzilla was freed by the Gotengo in Antarctica, Anguirus was deployed to the Japanese countryside with Rodan and King Caesar by the Xilien UFOs α, ß and γ, and waited to encounter Godzilla. When Godzilla arrived, Anguirus almost-immediately curled up into a ball and tried to ram Godzilla, but Godzilla used this to his advantage, kicking Anguirus into King Caesar and Rodan several times to knock them both out. Anguirus was also knocked out during the fight. For reasons unknown, Godzilla chose to spare the three monsters, and continued to follow the Gotengo towards Tokyo, where the final battle awaited.

Trivia

 * WatchMojo put Anguirus as #5 on their Top 10 Godzilla Villains List.