This is part of my English work... I'd like to know which leaders during the 21st century remind you of Stalin. (They could be leaders now e.g. David Cameron, Barack Obama and so on).
No one could (and hopefully will never) come close to Stalin. As bad as Hitler was, Stalin was worse -- if the mortality rates in the Soviet Union are even remotely correct for the era in which he was in power.
Any of the leaders of the totalitarian states that still exist in the world have similarities (like North Korea's late Kim Jong-il) but all are rather pale comparisons.
One dictator who openly admitted his admiration for Stalin, and modeled his political (though not his economic) practices after him was Saddam Hussein. His creation of a police state, mass murder in dissident regions, and liquidation of the opposition were all shared traits even if he did not operate on anywhere near the same scale as the Soviet leader.
Vladamir Putin, in that he was "re-elected" president by a whopping margin. I think it was in the 80 percents. That's a little fishy. I would be willing to bet that something is going on there. And what about the government of North Korea?
I don't think that any democratic leaders (like Cameron or Obama) could possibly remind one of Stalin. They lack the power and they have not done anything nearly as ruthless as Stalin did. Right now, the only one I can think of is Assad in Syria. He is willing to kill his own people to keep power. He doesn't have his country as much under control as Stalin did, but he is ruthless enough to qualify.