Here is a small list of the three most brutal human leaders to a civilization ever known. It is impossible to rank them in proper order for their horrible crimes but here is a list.
1. Adolf Hitler (1889-1945), he was one of the most brutal mans to step a foot on the planet. He destroyed so many Jewish families, villages. He also ordered the deaths of disabled people, homosexuals and Gypsyies. He thought he achieved his dream, he nearly eliminated all the Jews in Europe or forced them to run away. Hitler took lots of pride in taking out the helpless but he did also murder other Nazi Leaders like Rohm.
2. Joseph Stalin(1879-1953), the word merciless cannot be in a phrase without Stalin. The leader of the communist party of Russia and later Prime Minister. He wanted to turn anyone possible into a soldier, farmers, artistes anything. This process caused the death of 100,000 people. He ordered the death of Sergei Kirov, his only opposition. He sent around a millions of Russians to death camps. He even blinded the architects who made his beautiful temple in Moscow. The amount of deaths he caused are around 10million, even probably more.
3.Mao Ze Dong(1893-1976), a young revolutionist he was. He never assassinated anyone or took fun in killing others. But he did cause lots of civil warfare between different groups, social reforms. He also brought lots of famines into China, which caused most of the population to grow cannibal. He inspired humiliation which caused mass suicides. In 1960s he attacked intellectuals and privileged individuals.