Um... yeah. How about... you know, we just purge you with some fire instead of all that nonsense? I mean, I know how this sounds, but think about it. Doesn't that sound like great fun for everyone? I say, quality time right there. It will certainly burn right into your memory, and I'm sure you won't forget it for the rest of your life. In the end we could even gather around the fireplace and sing some songs together if we feel like it. And when it's all done, you won't even need to help cleaning up all the mess , it's like a win win for all of us! I know I would enjoy that.
Hmm but if the whole galaxy burns then what do we have left to kill? Maybe this is way chaos does not want everything to die all at once because all four gods need things and if everyone is dead then the gods have nothing to feed on. so we can look at the Imperium like a farm. We take what we need to eat and then let the harvest wait to grow again. Then we come back to reap once more.