It’s been tried and done before via chemical and biological methods (if you don’t want to sleep for awhile, check out what has been declassified on THOSE topics and realize that is what they were OK releasing to the public!).
The problem of course is that in deploying it, you’ll inevitably kill a bunch of your own - no population is so consistent you won’t kill a bunch of senior leaders who had parents 3 generations ago who were transracial or whatever and lied about it - and it will inevitably turn everyone in the world against you.
Even states like NK or Iran need friends, and those friends would have enough casualties from anything like this there is no scenario I can imagine anyone would intentionally release something like that.
Doesn’t mean a mad scientist type would cook it up accidentally in the garage, but there are always real world constraints stopping wide spread (physics sometimes, often effectiveness limits or the like).