The Godzilla species. Same powers as the original, can reproduce asexually, lay eggs that fill the entirety of Madison Square Garden in an insanely fast amount of time (the movie never clearly specifies if hours, minutes, months, or days had passed), and can appear and disappear within the blink of an eye and without a sound.
Consider the ecological implications and you realize that this is a potential End of the World scenario as the Godzilla species reproduces so rapidly that they'd probably eat the rest the earth's life into extinction within just a couple generations.
The unmade sequel's script actually addresses this. Specifically that not all Godzillas live to adulthood. By the time the survivor is found in the Australian Outback, it has reproduced — though there are only about 20 Godzillas there. The rest died of natural causes, such as being killed by predators.
Wait, predators? Even just hatched, they're akin to the full grown raptors in Jurassic Park, fully capable of hunting down heavily armed mercenaries. Just what the hell managed to kill them?
Have you never been to the Australian Outback? Even if they weren't taken out by some apex predator, they could have easily eaten things that were poisonous to them.
The Baby Godzillas are kinda rather terrifying. There are just so damn many of them and they all hunt down, kill and devour Philippe's men.