Amelia Dyer. Hanged for murder in 1896. Some estimate her victims to be 400 victims. All babies. This would make her the most prolific serial killer in history. She would take in the illegitimate babies of Victorian women, promising to “farm” them out to adoptive parents for a price, or raise them until the mother could return for them. She’d then pocket the money, pawn the baby’s clothes, and strangle the babies.