这颗小行星被标记为潜在的行星杀手，因为它的大小足以摧毁整个生态系统。

The asteroid was labeled as a potential ___planet killer due to its size capable of wiping out entire ecosystems.

这种新型除草剂被称为农业生态系统的毁灭者。

This new herbicide was called a ___planet killer for agricultural ecosystems.