You folks are forgetting all of NK chemical and bio weapons. If they come hard that will be first.
But I have heard rumors that we (South Korea and the US) have plans for that also.
Again, massive casualties in the first wave. Big hurt for the North soon after.
And remember, Russia is building up troops on the NK border. They are not real good friends, and have no desire to see a nuclear war in their (Russia's) back forty.
You are right, they will use everything they have hard and fast, And they have the knowledge they have nothing to fear from the zero regime. We are talking about what we COULD do to them. We won’t.