Well N Korea- Not a sane fellow at the best of times
Pakistan after the terror attacks in Mumbai sponsored in part by Pakistani Intelligence a war was narrowly averted, thanks to India who kept their cool
Russia who has stated they are a first use but limited option for deescalation. Deescalation, really.
Why Russia calls a limited nuclear strike "de-escalation" | Bulletin of the Atomic Scientists
The doctrine introduced the notion of de-escalation—a strategy envisioning the threat of a limited nuclear strike that would force an opponent to accept a return to the status quo ante. Such a threat is envisioned as deterring the United States and its allies from involvement in conflicts in which Russia has an important stake, and in this sense is essentially defensive. Yet, to be effective, such a threat also must be credible. To that end, all large-scale military exercises that Russia conducted beginning in 2000 featured simulations of limited nuclear strikes.