Jane Toppan "Jolly Jane" - One of the most prolific female serial killers who killed over 70 people. She thought of herself as "The Angel of Death" for good reason. She experimented on patients with atropine, strychnine and morphine.
Holmes and he is also thought to be THE Jack the Ripper because he was in London at the exact same time and was a medical professional. He went to medical school to learn how to kill people. He is scary.
In November Ronald DeFeo murdered his entire family, shooting them all with a Marlin Rifle. According to DeFeo he was being controlled by evil spirits and heard voices in his home in Amityville, NY. He was sentenced to six life sentences.