Ukraine

I very highly doubt that Putin would do this. Putin isn't a genius, but he's nowhere near being an idiot. He knows if he did that, Russia would die with the rest of the world. And he's never given any sort of hint that he's the kind of person that wants the whole world to die with him.

Not only that, but like the United States, it isn't actually Putin who launches the nukes. And there are historical instances of Russian nuclear officers refusing to launch nukes. I honestly trust the warmongering, imperialist dictator Putin not to launch more than I trust our own president, and that's terrifying to think about. Because Trump IS exactly the sort of person to order a nuclear launch because he's throwing a hissy fit and believes the myth of American exceptionalism.