Divinity 2: 1 turn Braccus kill

Obviously, before the fight, you side with Lucian and promise to give up your Source so you only have to fight Braccus. Then this setup will easily kill him in a single turn. If it doesn't, then you're still mostly safe thanks to invisibility; the only risk is dying before you even get a turn but I don't think that's very likely, especially if you equip a Toy Shield and get 3000 magic armor.