Joachim Kroll, the "Ruhr Cannibal," terrorized West Germany for over 20 years, eating the flesh of his victims because "meat was expensive."

Throughout early 1800s Delaware and Maryland, Patty Cannon and her murderous gang kidnapped as many as 3,000 Black Americans to sell into bondage in the South.

If his own confession before his brutal execution is to be believed, then Peter Niers slaughtered 544 people — 24 of which were pregnant women he killed for their fetuses.