In many ways, these two men were similar. Their main similarity lay in the fact that both were trying to create totalitarian regimes that they could control. Both men wanted their government to control every possible aspect of their people's lives. They used secret police, for example, to make sure that people did not hold (or at least express) any "incorrect" opinions. Both were willing to kill huge numbers of people that they saw as threats. In addition, both men were trying to create systems where all significant power lay in their hands. Thus, although communism and Nazism were not the same thing, Stalin and Hitler were both trying to create very similar systems.
thanks Mr. pohnpei ^_^