There is a lot of similarities between Putin and Hitler. Both controlling who won't stop until the get what they want. And they're never happy with what they have, so that's why I can see this escalating as much as WW2 did
The difference with Germany is that they were strengthening themselves during the time. Make no mistake, if hitler had stepped down in 1938 he would have been labelled as one of the modern great leaders for how he accelerated Germany's growth.
He done that though on a war economy, building armies/tanks/planes/ships. It meant he had to use them. Marching into the Rhineland and Czechoslovakia and the like was fine but he needed a war. Thats why he went to poland and attacked them.
but up until Poland he was restoring Germany's pride and position which was something not to be sniffed at. Combined with the art and culture and bringing things in like the autobahn Germany became ahead of its time.
I truely believe his downfall was him becoming power mad. Attacking Russia was done out of nothing but his idealistic beliefs and if he hadn't done that then europe would have been in his control by 1945. I also believe that the terrible things he is responsible for (and rightly so) was not his doing. I believe it was a simple chain of command order to do the things that happened which was built on his beliefs, almost like a religion. By all means he is rightly held accountable for that happening and history will show him as the person he really was but by 1943 he had lost his mind and bunkered up in Berlin he lost the total control he once had.