Hitler and Stalin both rose to, and consolidated their power through a combination of ruthless politics and violence. Both men, once in power, purged their opponents, some of whom had been their allies on the way up. Hitler, for instance, had many of the leaders of his paramilitary "brownshirts" murdered, and Stalin's infamous purges were a naked attempt to solidify his control over the Soviet government. Additionally, both men skillfully used propaganda and a state bureaucracy to strengthen their one-party control. Both established police states, shipping dissidents, imagined or otherwise, to concentration camps and gulags. Both men murdered millions of people, Hitler in the Holocaust and Stalin as part of forced collectivization, as well as the brutal purges.
Their differences were in the area of ideology as well as how they organized the societies they controlled. As a communist, Stalin's collectivization efforts, mentioned above, were part of his attempts to rapidly industrialize, taking control of peasant collective farms in an effort to support enormous government-run factories in the cities. Hitler, on the other hand, also set quotas for manufacturing, but forged alliances with industrial capitalists by allowing private ownership of factories. Indeed, part of Hitler's appeal to German elites was his opposition to Bolshevism. Hitler also emphasized a higly racialized form of nationalism, where Stalin, at least in theory, espoused a theory of communist revolution that rejected race and nation as constructs of capitalist society.