Have you ever used Kaiju in your game? I realize that D&D has things like dragons and other huge, gargantuan, and colossal beasts that are kaiju-like but I'm just curious if anyone has ever done anything kaiju-related in their games.
The Bestiary 4 for Pathfinder contains kaiju stats. Nothing official exists in, but if you want to include kaiju there's a product on the DM's Guild site that may interest you. Gargantuas of Kara-Tur 5E updates Gargantuas (essentially Kaiju) from the Kara-Tur Monster Compendium to 5th edition. At only two dollars, the product doesn't have a lot of content, but it still gives you four varieties and something to work from when making your own. The four different gargantua represented are reptillian (Godzilla), humanoid (King Kong), insectoid (Mothra) and Krakentua (the Cthulhu in a kimono to the right). I've not used them yet, but they seem reasonably well balanced.