At least Loki was freed. We could have ended up like Prometheus, having his innards ripped out and growing back for eternity.
Forgot the name, but the guy that has to roll the rock up the hill for eternity...gets it almost to the top before it rolls back down. Or, like those folks in the pool of water, suffering from eternal thirst.
Waking up to discover I was injured somehow, and I'm now trapped, fully conscious, in an apparently comatose body. I can hear everything, but I have no voluntary muscle function at all. I can't even focus my eyes, much less move them. They can tell from an EEG that I'm not brain-dead, but that's all.
Trapped in a non-responsive body, unable to communicate, for as long as they can keep me alive. That is my worst-case nightmare.