Devourer of worlds

Orbital bombardment would be far too blunt to damage a planet, it would take an astronomical amount of force to punch through its crust, while digging in and poisoning it from the inside, or causing any number of medical problems, would take much less effort, it's like killing someone with a baseball bat versus a poison. Both work, one takes a bit more planning, the other takes more energy.

As for the coding bit, these could just be triggered events, break x blocks in this region, pump x blocks of n toxin into it, kill x mobs in this area and there's a planetary event that causes the planet's biome to change from ''live'' to ''dead''

 

You obviously don't know what kind of explosives I use.

(A digging explosive that's more powerful than a nuclear bomb that digs into the center of the planet and violently detonates itself causing the planet's crust to shift, crack, and eventually crumble.)
(Look up exterminatus on the warhammer 40k wiki.)

 

into the guts of a living planet... me likey 8)

 

Mmmh... what? I like your idea (or at least i think so... ) but next time translate it for yourself instead of using google translator.
I like the idea of landing on a huge monster.
It could be a huge bloody dungeon, where you have to enter from it's mouth (or another orifice if you prefer...) and make your way through its organs (it'll try to digest you with his acid) to destroy its brain/heart/nucleus/whatever (its guardian object -> if you don't destroy it, you cannot mine blocks). Then prepare a camp fire somewhere and roast some meat blocks! ITADAKIMASU!