Given I've been on the subject the last two weeks, I thought I'd step up me game, as it were. Not to be confused with ecocide, the destruction of the ecosystem, or omnicide, the killing of everyone -- this is the killing of the whole planet. Or if you live in a science fiction universe with a planet-buster or a Death Star at your command, an entire world. This may of course, involve genocide, the killing of an entire ethnic or national group, and that may even be the goal of the destruction. Like most -cidal words, coined from Latin roots -- mundus meaning word.
Many world religions have stories of the gods attempting mundicide, usually by flood or fire.