People you consider more evil than Hitler

[GeneralMacArthur]

You can make a pretty decent case for Pol Pot and Mao Zedong.  Like Hitler, they harbored and intense hatred towards particular groups of people, and when given the power to act on that hatred, implemented a policy of widespread industrialized mass-slaughter, while simultaneously using the oppressive power of the state to try and brainwash their entire population into agreeing that the hated groups deserved to suffer and die.

If you were to make the case for those two as more evil than Hitler, it would be because while Hitler saw the Jews and other ethnicities as an inferior race, and worked to torture and murder them en masse, he saw his own German people as a superior race that he wanted to build his Aryan utopia for.  Similar to Hitler, Mao and Pol Pot harbored intense hatred for intellectuals, landowners, peasants with too many chickens, teachers, businessmen, wrongthinkers, people who wore glasses, etc. and endeavored to torture and murder them.  But they also saw the rest of their people as just idiotic swine to be pacified and abused.

Even if you weren't a class enemy in the People's Republic of China, you still ran the risk of having all your property stolen, being humiliated in the street and tortured into submission, and then turned into a slave for Mao's latest idiotic project while you watched your family starve to death, which Mao would simply mark as another number on a sheet of paper.

Even if you weren't an intellectual or ethnic minority in Democratic Kampuchea, you would still be forced at gunpoint to surrender all your possessions and march out to some swampland where you'd slowly be worked and starved to death while your children were abducted and taken to an indoctrination center to be turned into slaves for the state, if they were lucky enough to not be used for horrifying medical experiments or sexual slavery.

Is that more evil than Hitler?  It's an extremely high bar to clear, but the case could definitely be made.