Eels that snuggle up to the heat pipes and suck up the heat instead of destroying anything.
A planet with large tornados spawning and slowly roaming about randomly. They would need to be dispersed by shooting artillery at them.
Deadly plants that spread to adjacent tiles slowly covering the entire map, can't be that UPS intensive if done in a certain way.
Invisible virus that takes over your gun turrets and starts constructing random shit using a shitty auto-factorio script.