King Leopold II of Belgium . Is this man not recognized as a mass murderer? If not why?

I've just seen a documentary of how this guy colonized Congo/Zaire and killed 10 to 15 million people which took place in 1885 to 1908. During the documentary goes on and talks about how Europe forgot about the genocide or holocaust. Should the world know about this? I mean this guy made Slobodan Milosevic look like Jimmy Cartar and Hitler look like........well Slobodan Melosevic.