Godzilla

Godzilla ("Gojira" in Japanese) is a fictional Japanese film character from a long line of films about him that started in 1954. He is a giant monster (or "Kaiju" in Japan). He was created by filmmaker Ishiro Honda, FX man Eiji Tsubaraya and producer Tomoyuki Tanaka in the 1954 film GOJIRA (or as it was called in the USA "Godzilla, King Of The Monsters").

Background
He was a dinosaur that lived in the sea near Japan that was mutated by H-bomb tests into a fire breathing monster.

Powers
Breaths underwater.

Blasts fire from his mouth.

Can not be killed by gunfire from tanks, jets, cannons etc, etc.