Most sinister thing in Anbennar

I'm just wondering, what's the most awful, sinister thing you can do that has an impact to the world? Not like slain half of your pops for a buff or sth, but, hmm, something like drop a magical nuke on Anbenncost and make it perish or sth, idk, just something that is not only lore-wise but also in eu4 mechanics totally sinister to other countries in the region/world