Re:"Mother Nature[..]'s self-regulation [..] has kept this planet alive for millennia"
Mother Nature has already programmed the death of this planet. It is called the Red Giant phase of our Sun, and it will happen in 5 or 6 billion years (give or take a few hundred million or so).
Before that date, nothing short of a direct collision with a wayward planet can possibly destroy Planet Earth.
Concerning Life on this planet, however, a number of things can destroy it with great efficiency. A stray Gamma-Ray Burst pointed right at us can boil the ozone in the atmosphere, thus exposing all life to drastically increased levels of UV radiation. Cancer and genetic changes will abound as life struggles to adapt. Most will fail, including probably humans.
A large asteroid, anywhere above 5 km in diameter, will most probably wipe out all life on the surface of the planet, leaving the deepest parts of the oceans as possible havens for whatever is left.
Those are just two ways that Mother Nature can put an end to life on Earth.
But Earth itself will endure. And life will most probably reappear whatever happens, as even in the worst-case scenario a propitious asteroid can re-seed the planet with the required building blocks.