How does one annihilate a planet..?

I didn't expect to find Homestucks here

Personally, I don't see anything wrong with hitting a planet with a large space rock to render it functionally destroyed. Bonus points for filling that giant space rock with explosives (While using the mined material to lob smaller rocks at the planet with a decent speed) and detonating it a bit after impact, vaguely similar to a bunker buster.

Those are the (relatively) quicker and (significantly) more impressive ways of doing it, of course. An orbital ring (or two plus, different orbits and all) of satellites with high energy lasers to cut the planet open has a certain appeal. Heck, if you get your orbit right, you can (attempt to) cut neat holes in the planet.

How does one Annihilate a planet?
Well first you define 'Annihilate'.
Do you mean catastrophic energy dump to overcome the gravitational binding energy of the mass? (Hit it with a large blunt instrument)
Or merely render it's surface unusable? (slow thermal dump into the mass eventually leading to the re-liquefaction of the surface, -Solar death-ray BTW)
Or do you mean to simply scour the existing force off in a single strike? (MUCH smaller KE strike)

All of the above seem viable. as depicted in the kick-starter they plan to have giant thrust units to move asteroids; simply mount a lot of them to move the planet? Maybe into a gas giant or the sun?

Each is much better for a given circumstance.
-Impactor (big): fast, good for sneak attacks. Has the problem of being diverted.
-Impactor (smaller): very fast, so fast you either anticipate it or it hits you (as it does not need a solar slingshot to nail you. Limited hit power (bunkers may survive)
-Solar (or any other power source) death ray: very slow, but as it is an energy strike the opponents MUST come up there and stop you. It does however have high setup time/cost.
-Precision Impactor: well basically it is just orbital artillery. Would be handy on that Deathstar though (see below)
-Deathstar: :twisted: ... well maybe not the Superlaser toting one but an asteroid fortress loaded with nuclear silos can be easily built and orbit shifted over the target for a few orbits of raining nuclear mayhem (it's even reusable! - Go GREEN!). But as the thing was never even meant to impact it would be pretty easy to nuke it back...
-Core bomb (at lower power a crust inversion event.. The floor is lava Planetary edition): well you have to deliver the bomb into the target AND not be there when you say boom! This one can be pretty stealthy though, but slow and expensive (that would be one hell of a bomb to build!)
-Engines: um... unless you are planning to use the :shock: !WHOLE PLANET! :shock: as an asteroid fortress (that would be a hell of a lot of nukes/anti-nukes) this one is probably just plain showing off given the radical resource/time effort needed
-Engines as spin-up? well that would be neat and it would work. But unless you have a means of choosing how it breaks up it is ultimately... meh. If you CAN choose how it breaks up though... Well a planet would produce very many large impactors, and somehow they all seem to have large engines already attached. I dub thee the Solar System Shotgun! (SSS). Hit ALL the planets with Impactors! No mercy! No survivors!

So there ya go. If I think of any more I'll list 'em

P.S. for inquiring minds I am the Achronus of over on GPG forums (someone has already registered 'Achronus' so I am stuck with TheAchronus)