Wiping out all life on Earth is hard, but causing mass extinctions is easy. Asteroid/comet strike: a giant impact triggered the last great mass extinction 65 million years ago. Comet Swift-Tuttle, which could strike Earth in 4479, carries 28 times the destructive energy of that event. If one occurred within 6,000 light-years of Earth, it would destroy our ozone layer, causing a mass extinction. After 2 billion years, the Sun's increasing energy output will boil the oceans, unambiguously terminating all life on Earth.

Source: Forbes March 18, 2019 06:00 UTC