A planet is hanging in space, where it technically weighs less than 1 lb (just put it on a small scale, and see what the scale reads), so you can paint an explosive rune on it, and set it off.
Voila.
Also, take a massive tarp into space, paint a ginormous explosive rune on it (with Explosive Spell applied), then drape it over the moon. The first person to read the rune will set it off, which will blast the entire planet away (since it affects all creatures and objects capable of seeing it once it explodes, so Explosive Spell will blow everyone and everything that doesn't make its save thousands of miles away...and unattended nonmagical objects [such as a planet] can't make saving throws).
Also, if destroying every creature on the planet counts, there's always the wightocalypse.
Iron heart surge it away, since it's affecting you with its gravity.
Also, d2 crusader it to smithereens.