Mutually Assured Destruction has been around for so long that nobody can possibly win in Nuclear War. In fact, Ukraine is a nation with Nuclear capacity, since they obtained 1,700+ Soviet Era nuclear weapons upon their independence in 1991. If Russia was going to pull the Nuclear War card they would have done so a long ass time ago.

If Russia Attacks a much stronger nation than Ukraine like Finland, then we know exactly what will happen. The will be absolutely decimated in land and population to say the least. Modern Russia was always a paper tiger but it has become even weaker with its failed invasion.