North Korea’s leader, Kim Jong Un, ramped up the rhetoric that has increasingly soured relations between South Korea, promising it would use “all the offensive forces it has possessed, including nuclear weapons”. South Korea responded that its US-backed response would be “overwhelming” and result in the “end of the North Korean regime.”
Agreed. Though the challenge is more getting it airborne at all.
NK likely has shotgun nukes. These rely on spontaneous detonation, when above a critical point. The are big, heavy and awkward. The 2 big innovations with nuclear weapons were compression nukes, and hydrogen bombs. These both require far more engineering than a shotgun nuke. However it also allows them to be far smaller.
NK has nukes. It also has MRBMs. What it doesn’t likely have is an MRBM or SRBM capable of lifting their nukes remotely reliably. If NK was to deploy a nuke, it would more likely be via a container on a flatbed lorry than a missile.