Destroying the Earth is harder than you may have been led to believe.
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.
This is not a guide for wusses whose aim is merely to wipe out humanity. I (Sam Hughes) can in no way guarantee the complete extinction of the human race via any of these methods, real or imaginary. Humanity is wily and resourceful, and many of the methods outlined below will take many years to even become available, let alone implement, by which time mankind may well have spread to other planets; indeed, other star systems. If total human genocide is your ultimate goal, you are reading the wrong document. There are far more efficient ways of doing this, many which are available and feasible RIGHT NOW. Nor is this a guide for those wanting to annihilate everything from single-celled life upwards, render Earth uninhabitable or simply conquer it. These are trivial goals in comparison.
This is a guide for those who do not want the Earth to be there anymore.
For the purposes of what I hope to be a technically and scientifically accurate document, I will define our goal thus: by any means necessary, to render the Earth into a form in which it may no longer be considered a planet. Such forms include, but are most definitely not limited to: two or more planets; any number of smaller asteroids; a quantum singularity; a dust cloud.
Hah, at last good practical information. Mad they called me. Fools, I'll Destroy Them All! BWA-HA-HA-HAAA!