Adolf Hitler and Joseph Stalin were the most influential dictators of the XX century who to a very significant extent shaped it. Both used very similar methods (including some purely criminal ones) to achieve their fundamental objectives.
Which were radically different, though. Adolf Hitler wanted to make Germany a secure, prosperous and genuinely happy nation (at the expense of other nations) while Joseph Stalin wanted to acquire unlimited power over the maximum number of nations and individuals (ideally, over the whole world).
Although the former objective was far nobler than the latter, it produced strikingly similar results. Both mega-projects ultimately contributed to the outbreak of the World War II which resulted in millions dead and injured in Germany and in the Soviet Union (and in many other nations), colossal devastation on an unprecedented scale in both nations (and in many other countries) and in horrific war crimes and crimes against humanity.
Both dictators met a miserable end. Adolf Hitler committed suicide in his bunker having lost the war that he has ignited six years prior and Joseph Stalin was directly or indirectly murdered by his henchmen and died in a pool of his own urine.