The real one that you won't hear is the Europeans genocide of over 100 million Natives, but it occurred over a long period of time. Here are the 3 largest genocides from 1900-2000:
Mao Tse-Tung (China, 1958-61 and 1966-69, Tibet 1949-50) - 49 to 78 million
Josef Stalin (USSR, 1932-39) - 23 million (the purges plus Ukraine's famine)
Adolf Hitler (Germany, 1939-1945) - 11 to 17 million (concentration camps with Jews, homosexuals, Gypsies, Soviet POW's, and in some cases other innocent German civilians)
only the most famous genocide in human history though sadly not the only one.
Stalin, Hitler and Mao
circassian
That he was a tyrant, psychopath and a fiend. Don't forget hitler initiated the hollacaust which was the largest case of mass genocide in modern history.
The Jews.
Yes. Unfortunately, both Anti-Semitism and genocide were quite common in Jewish history.
the trans-atlantic slave trade, also known as the Atlantic slave trade. It was the largest and one of the cruellest displacement of people in the world's history.
Probably the largest number ever in the history of time
No.
industiral revolution
it was one of the largest human migrations in history
It was the largest and most devastating war in human history.