|Political power growing from the barrel of a gun, communist style (Source)|
At an estimated 100,000,000 dead from communism in just the 20th Century, the Wall Street Journal has referred to it as "the greatest catastrophe in human history." The 100 million estimate is generally traced back to the Black Book of Communism which estimated 94 million dead due to communism in the 20th Century. However, there are critics of the book, who have referred to as propaganda because it may have only (only!) been 65 million killed. But I have also seen much higher estimates, and one mid-estimate is 149,469,610. The latter estimate is higher than the Black Book because it includes more communist countries in its count.