My Idea of Godzilla as a TF2 (+ Half-Life & Portal) Character.

Rather than being mutated from a nuclear screw-up (like 1954 Goji & Castle Bravo or Shin Goji & that 2011(?) Atomic Power-Plant Earthquake), this Godzilla was intentionally created in the early Cold-War by an obscure Genetic Research branch of MannCo for the purpose of keeping Australia safe in case the US-Russian Cold-War got Hot.

Formed as an Australium-Eating Clone-Hybrid of a Bear, Iguana, & Salamander, Godzilla was raised mostly on a Spartan-Upbringing, but at least being taught Basic Mathematics & Probability (nonetheless for the purpose of fighting).

Unfortunately, a Clumsy Janitor accidentally knocks over a Can of Bonk Uber-Cider (BONK Version of Dr Pepper) into Godzilla's Enclosure, prompting Godzilla to lick some off of a Rock, immediately become Smarter than any Human whilst Uber-Charging the creature until he grew to the Size of a Building. Godzilla lays waste to the Laboratory & Escapes into the Ocean, where he would spend his days consuming Geothermal Radiation to produce his own supply of Australium - essentially Radio-Synthesis or Nucleosynthesis, if that makes sense.

As for how he was named "Godzilla," he did end up rampaging through somewhere in Okinawa (mainly to steal fish from fishing vessels) where a human there refers to the Beast as "Gojira," mistaking it for a Gorilla-Whale beast (reference to origin of name) based on his Roar. Gojira sounded like a gnarly name of Terror, but Godzilla sounded much more Powerful - amplifying the fear factor beyond anything imaginable by Humans. "Godzilla" would be a Signature engraved in any rubble wherever the Beast left havoc in his wake.

When the Combine Invaded before HL2, G-Man sealed Godzilla away within the Earth, putting him in a State of a Death-Like Sleep (G-Man is a vague prick, so this kinda makes sense for being vague too)