But you’re not balancing the game. You’re not adding a powerful BBEG. You’re putting a GOD in their path specifically to threaten the players into submission, even goading the players into action with that little “try it, bitch”. You’re showing the exact same antagonism, desrespect for the world and propensity for violence as the players are. I don’t care who did it first.
Just fucking talk to them. Like people do. Say “hey, maybe turn down the murdurhoboing?” instead of jumping to killing them. It’s the DM’s job to mediate the game and solve disputes as they arise so everyone has fun. Do your fucking job.
Edit: It’s always funny how unreasonably upset people get when you suggest talking through problems in a game played entirely through talking.