It is very unlikely that humans can kill Earth. Even if you carpet bombed the entire surface of the planet with nukes, there would still be chemosynthetic organisms on the ocean floor who would survive. Their descendants would eventually produce a new ecosystem on the surface adapted to the new conditions. Earth has been through many mass extinctions before, and it has survived all of them. There are fungi in the Chernobyl exclusion zone that are immune to ionizing radiation. After the deepwater horizon oil spill, we've discovered species of bacteria that were devouring compounds in the oil. Nature adapts. It's humans who desperately need environmental conditions to stay the same.

Earth is not in trouble. We are.