I’m struggling with overly confident players. Obviously, killing a PC is one way to make them think twice about the next time they pick a fight, but I don’t want to resort to that if I don’t have to. Is there a long term status condition or something I can subject them to that’s good at making players averse to picking fights, even when they think they can win?
Not every fight has to end in death: have an encounter with enemies motivated to capture PCs (ransom, perhaps, or simply averse to killing), and have them do so when a PC goes down.
If it’s a TPK then they have to break out of captivity, or possibly negotiate their release in exchange for solving a problem for their captors. If only one or two PCs go down then the remaining members might have to find a way to pay the ransom, or find a way to break them out. If it’s mixed, then maybe it’s a coordinated jailbreak with PCs working together from inside and outside.
Fun scenario, but a giant pain in the butt for whatever other goals they had in the campaign, and a great wakeup to “hey, maybe I shouldn’t just be bulling into every fight”. You can steer towards a solution that doesn’t involve fighting as well, to give them a forced crash course in their characters’ nonviolent capabilities.