Adolf Hitler, Joseph Stalin, et al, all had certain biological traits
shared with the rest of humanity.
Now those same traits and features may be present in all homo sapiens. Certainly some are, like the reptilian cortex found in all humans.
But for the most part these lay genetically/socially dormant or manifest themselves in other more positive ways.
I'm amazed to read that many human beings, many who think
themselves civilized and good can be whipped up into a violent mob
frenzy under the right conditions. Think 1789-1793...1917...1933, etc.
It all makes me wonder if humans may be the deadly virus
in the universe whose other inhabitants may well wish
to have nothing to with us.