I realize I may get some divisive answers, but if NATO Countries all agreed, mobilized, and went into Russia full force with no warning, what are the likely outcomes?

EDIT: For clarification, I feel that the current situation on the ground in the war (vs. say a year ago) might indicate that an attack on Russia might not result in instant nuclear war, which is what prompted my question. I am well aware of the “instant nuclear Armageddon” opinion.

Serious question. I don’t need to be called stupid. I realize nuclear war is bad. Thanks!