Amelia Dyer was the most prolific baby farm murderer of Victorian England. She was tried and hanged for one murder, but there is little doubt she was responsible for many more similar deaths - possibly 400 or more - over a period of perhaps twenty years.
Elizabeth Bathory - Lady Dracula AKA the Blood Countess. She was related to Vlad Tepes, Dracula. She died by being bricked up into a bedroom so she couldn't leave & commit murder against the village girls.
Lizzie Borden was acquitted of the murders of her father and stepmother. Andrew Borden and Abby Borden were brutally murdered on August in Fall River, Massachusetts. Lizzie Borden was arrested for the murders a week later.