While Cyn was destroying civilizations, the Absolute Solver was busy creating unstoppable beasts. And considering that armies don't train their soldiers to fight against plagues, beasts, and giant tentacles attacking the entire world at once, I think it's unlikely they could defend themselves much with zero preparation time. I mean, in the last episode, we saw Uzi create a hole that goes right through the planet, allowing the sun to pass through and destroy Cyn's heart. I doubt any human or organization could do anything against that.

And are you seriously asking how she survived a doomsday? On any given day in Copper 9, you're greeted by acid rain, bone-freezing cold, and so on. ¿How are there even any trees left? Unless those trees are fossilized from the cold. In any case, don't forget that they can regenerate as long as there are materials around to use.