In one of my forts I've still kept a previous save file to a few months before this monstrous thing happened, I guess it was inevitable considering the cruel things I had done.
I started this fortress like any other, when i got migrants I had this peasant who was so similar to Hitler in his preferences I named him after him. There the bloodbath began, I proceeded with plan: make the entire world your enemy. I had about 1000+ food with 18 people, and merchants came, dwarven merchants, here's where my hell began. They sought trade with me, however my dwarves would refuse to go to the trade depot although i had 2 idlers (actually on break) therefore I commenced Stage one of making an enemy of the entire world; I started blocking off access to the Trade Depot with floodgates, the dwarven merchants still being in there, eventually they died of thirst. The next time dwarven merchants came was probably the last. I left them in there, thinking all the stark raving mad ones had died I proceeded to unblock the floodgates, I was so wrong... so wrong.. One still quiet alive merchant came out, stark raving mad of course, his military instantly ran away, him with one leg started brutally murdering dwarven babies in my stockpile area. Tantrum spiral. Dwarves had made an arena out of my stockpile. Gladiator arena. Two dwarves survived the mess, a miner and a carpenter. Abandon Fortress.
Much facepalm here. Yes, I felt horrible for letting dwarves die.