Kaiju

Outside of isolated panics when the first millennium came around in 1000 A.D., most medieval millenarians (in both Christendom and Islam) reacted with ecstasy and fervor – admittedly, sometimes murderous ecstasy and fervor – whenever the Apocalypse seemed likely. Fear of the end of the world was merely epidemic, with fierce but brief outbreaks when a comet flashed or a charismatic mendicant appeared at the gate. 
It took the modern era to turn fear of apocalypse into a chronic state. The end of the Cold War merely replaced a nuclear apocalypse with an environmental one. The Y2K panic featured the idiot-god computer, with humanity locked into an unwilling suicide pact. Population paranoia created its own zombies, the ever-hungry, all-consuming Others. Global warming nightmares married fear of technology to poisoning phobia with a soupçon of cosmic horror. But it all began with the Bomb.
-- Fear of Apocalypse intro, GURPS HorrorGURPS Horror, p.94A kaiju is, in origin, a disaster made flesh. From the earliest giant monster movies, The Beast from 20,000 Fathoms (United States, 1953) and Gojira (Japan, 1954), kaiju have represented the raw destruction from mankind's most violent creation -- the Bomb. 
As fears evolve with society, kaiju evolve based on those fears. Kaiju are made with with bombs, or unmelted from glaciers, or fall from meteors. Sometimes they're developed in labs, as bioweapons or massive machines, or complete accidents. Whether created directly as a weapon, or indirectly through negligence, they represent the human cost of carelessness. At least, usually.
== The Exceptions that Prove the Rule ==
Not all kaiju are designed with "big meanings" front-and-center. Sometimes a big monster exists because someone thought it would look really cool.
== Stats ==
"Ordinary bullets have no effect, and a method of destroying the awesome creature has not yet been formulated." -- newscaster, The Beast From 20,000 Fathoms (1953)
=== Kaiju at Human Scale ===
==== Power of a God(zilla) ====
When fighting on human scale, being able to avoid a kaiju is more important than figuring out how much damage you need to kill it -- needing a special superweapon or other kaiju to defeat a kaiju is often what makes the genre. Kaiju tend to be "slow", moving at whatever pace matches the length of their stride -- when running however, the physics get weird. Godzilla and Ghidorah's charge in the Monsterverse was said to be 200 mph (Move 98) by the SFX team!See this article.
Kaiju will often have some immense level of supernatural DR and/or fantastical regeneration at their disposal -- these traits are often only bypassed by other giant monsters. If small arms do anything more than bother a kaiju, it may be classed as a "giant monster" than a "true kaiju". In this case, use Monster Hunters as inspiration, and be aware of Combat Writ Large for effects like huge feet vs cars and creatures.
==== Other Considerations ====
In a "lion and a thorn" situation, a kaiju may actually want a troubleshooting team, to rid them of human-sized parasites!
=== Kaiju at Kaiju Scale ===
It takes real world-shaker-class characters to take down a kaiju. They could be Supers, or other Kaiju, or people piloting huge mechaSupers, p.14 -- likely C-scale or M-scale!Supers, p.19 There's also attempts at mind-controlling or piloting kaiju through technology, although this is often done by villains -- a monster created by ignorance and negligence must be understood before it can be controlled.
== Rethinking the Kaiju ==
The themes of a kaiju can still work well in a smaller (perhaps, more "sewer gator" sized) package. Take any disaster or great folly and you can make a compact but thematically important creature that might fit in to a Monster Hunters adventure. 
* The Floodwader: This catfish-gator monster buries itself in silt for long periods of time, but is awoken when hurricanes flush it out from its den. The floodwader shows up when drainage systems, dams and levees have failed, making disasters even worse.
* The Uxomorph: This creature is somewhat like a baryonyx in size and shape, with large patches of skin in slightly different colors. It consumes landmines like a truffle-hunting pig, but its spines are just as dangerous. It doesn't eat the prey it kills, and seems to be immune to blasts.
* The Long Wolf: This creature looks part wolf and part weasel, and always looks like it's sick from something. It digs into trenches where it feeds opportunistically on the dead (and the dying) on the front lines of war (setting permitting). It grows throughout its lifetime and is seemingly immune to poison gas, making it an unwelcome third party to every no-man's-land.
== References ==