Launching a nuke only makes sense if Putin just wants to try and end the world? A tactical nuke isn't likely to change the strategic direction of the war, it's just escalation for the sake of escalation. He's already losing the war. Launching a nuke in Ukraine or NATO does not mean that NATO respond with nukes. They can respond with conventional weapons and end the war within a week.
Plus there's a non-zero chance that the chain of command refuses to carry out the order and undermines all internal authority that Putin has.
Plus there's a non-zero chance that the chain of command refuses to carry out the order and undermines all internal authority that Putin has.