Many historical figures are thought to be psychopaths, for example:

Julius Caesar
Adolph Hitler
Idi Amin
Napoleon
Alexander the Great
Robert Maxwell
The Kray twins
Frank Sinatra.
Another psychopath was Josef Stalin who was responsible for killing about 20% of the Russian population but millions of Russians still mourned his own death. President Roosevelt of the US completely misjudged Stalin's character and thought he was trustworthy and not a monster, thus allowing Stalin to manipulate him and get away with controlling Eastern Europe, precipitating 50 years of cold war between the US and the Soviet Union