From Sam's Archive : How To Destroy the Earth.
Destroying the Earth is harder than you may have been led to believe.But he provides a number of ways, anyway. Some require a bit of patience though.
You've seen the action movies where the bad guy threatens to destroy the Earth. You've heard people on the news claiming that the next nuclear war or cutting down rainforests or persisting in releasing hideous quantities of pollution into the atmosphere threatens to end the world.
The Earth was built to last. It is a 4,550,000,000-year-old, 5,973,600,000,000,000,000,000-tonne ball of iron. It has taken more devastating asteroid hits in its lifetime than you've had hot dinners, and lo, it still orbits merrily. So my first piece of advice to you, dear would-be Earth-destroyer, is: do NOT think this will be easy.
Method: If by some insane chance, the expansion of the Sun into its Red Giant stage does not destroy the Earth (perhaps somebody moved the Earth out of the way in time), then there's still no need to fret. Protons, while incredibly stable, eventually decay like any other particle. Simply wait for a period of time of the order of 1,000,000,000,000,000,000,000,000,000,000,000,000 years, and roughly half of the constituent particles of Earth will have decayed into positrons and pions. If that's still too much like a planet for you, you could wait for another 1036 years, leaving only a quarter of the original Earth. Or wait even longer. Eventually there will be as little of Earth left as you wish.