While Dean and Jack spent the episode powering Jack up to be ready to kill God (and Amara) when the time came, Sam and Castiel were trying to find a way to save him.
Spoilers ahead for Episode 17 of Supernatural Season 15, called “Unity.”
Supernatural may well be finished with the standalone monster hunts, because “Unity” took Team Free Will 2.0 and their battle against God past a point of no return.
Unfortunately, Jack lit his own figurative fuse before the end of the episode, and the credits rolled with him seemingly moments away from dying with Cas, Sam, and Dean by his side.