What if the Soviets had attacked Germany without Hitler? Would a weak Weimar Republic have been capable of defending against a potential Soviet invasion to Western Europe? If Germany had fallen without inflicting massive casualties, then it is possible that Soviets would've been capable of eventually conquering much of Europe. The scale of their armaments was beyond comprehension at the time, even way above Nazi Germany at their peak. A non-Nazi Germany, I'm afraid, would've been chewed up and spit out.
I believe that Germany required a Hitler'ish character at the time, to answer the Soviet threat, but one that would've been capable of convincing Britain, France and the United States to ally against the Soviets, instead of allying with the Soviets, to prevent Soviet expansionism to Eastern Europe. And preferably without the fascist excesses, of course.