MALEFACTOR, n. The chief factor in the progress of the human race.

Ambrose Bierce (1842-1914?) American writer and journalist

“Malefactor,” The Devil’s Dictionary (1911)
    (Source)

Originally published in the "Cynic's Word Book" column in the New York American (1904-08-06) and the "Cynic's Dictionary" column in the San Francisco Examiner (1904-08-19).