Although the thing about Hitler is that he wasn't just unappeasable (because he had ambitions of world domination), he was also undeterrable (except in the very short term, like when Mussolini deterred him from taking over Austria in 1934) because he was an extreme Social Darwinist who viewed human life (even German life) as inherently worthless.

dspace.mit.edu/bitstrea…

I don't believe that Putin is truly like Hitler in that respect, but wouldn't nuclear armageddon be unavoidable (short of being able to stop ICBMs with an SDI-type system) if he was?