Cordelia Botkin (1854 - 1910) In 1895, Cordelia Botkin — a married woman — started an affair with John Preston Dunning, also married. Their sordid affair lasted three years, until Dunning left Botkin and reunited with his wife. So Botkin decided to send her some chocolate. She sent it anonymously and — single-handedly proving why you should never take candy from strangers — laced the chocolate with arsenic. Mrs. Dunning and her sister were both killed, and the three people with whom she'd shared the candies were also sickened, but survived. Botkin's flaw, though, was that she'd written a note along with the chocolate, and her handwriting was matched to letters she'd written to Dunning and his wife detailing their affair. She was sentenced to life in prison, and died in 1910 in San Quentin.

Jane Toppan (1857 - 1938) Jane Toppan was a nurse at Cambridge Hospital in Boston. Her favorite hobby was experimenting on her patients with morphine and atropine to see what it'd do to their nervous systems. She also cuddled with her victims in their hospital beds while they died, later explaining that she was sexually aroused by death. She was eventually fired for her reckless opiate abuse, but soon got jobs as a private nurse and continued to poison just about everyone she came in contact with. She even poisoned herself to gain sympathy. She was eventually arrested, confessing to the murder of 31 people. She spent the rest of her life in a psychiatric hospital.

Joseph Vacher (1869 - 1898) After being released from a psychiatric hospital as "completely cured" in 1894, Vacher began a three-year killing streak, culminating in the deaths of 11 people — most of them shepherds watching over flocks alone. He sexually assaulted, stabbed, and dismembered his victims. This eventually earned him the nickname "The French Ripper" because his M.O. was similar to that of England's Jack the Ripper. He was arrested after his twelfth victim fought back, and readily confessed to the killings. He was executed for his crimes in 1898.

"The Servant Girl Annihilator" (event took place from 1884 to 1885) The name makes this sound like a really bad video game, but this was the name given to an unknown serial killer who preyed on servant women in Austin, Texas, while they slept in their beds. Seven women and one man were killed, and an additional six women and two men were seriously injured during the spree. Although more than 400 people were arrested on suspicion, the killer was never identified. The killings stopped abruptly on Christmas Eve of 1885. Three years later, Jack the Ripper terrorized London, leading some to believe that he and the Servant Girl Annihilator were the same person.

Bela Kiss (1877 - ?) When Kiss started collecting large metal drums and keeping them on his property, his neighbors thought he was stocking up on gasoline in preparation for WWI. In 1914, he was drafted and left for war. Two years later, a town constable remembered the drums on his property and offered their use to soldiers in need. When they opened them, though, they found that each drum actually contained the body of a strangled woman. There were 24 in total, and all had puncture marks on their necks, from which he drained their blood. They were then essentially pickled in alcohol. Kiss was to be arrested in a hospital where he was recovering, but he placed the body of a dead soldier in his bed and fled. He was never caught, though someone claimed to see him in Times Square in 1932.

Leonarda Cianciulli (1894 - 1970) Known as a loving wife, doting mother, and kind neighbor, people were shocked when this woman turned out to be responsible for the deaths of three women in Correggio, Italy. Extremely superstitious, she turned to killing when her son was drafted into the Italian army in WWII believing that only human sacrifices could ensure his safety. Not only did she drug, bludgeon, and dismember her three victims, but she also collected and dried their blood to bake into tea cakes. The third woman was turned into soap. All of Cianciulli's "handicrafts" were shared with friends and neighbors, earning her the nickname "The Soap Maker of Correggio." She died in a criminal asylum in 1970.

Henri Landru (1869 - 1922) Landru was considered to be the real life Bluebeard, who lured women — specifically widows — to his home and then killed them (only after they'd granted him access to their money, of course). Between 1914 and 1919, he killed 10 women, as well as one of their teenage sons. He used so many aliases and so many alibis that he had to keep a detailed ledger of it all, which eventually led to his capture and conviction. The ledger was all that the authorities had to go on, since Landru disposed of his victims by burning their bodies in his stove. He was executed in 1922, and his head is currently on display in the Museum of Death in Hollywood.

Fritz Haarmann (1879 - 1924) Haarmann was known as both the "Vampire" and "Wolf Man" of Hanover, Germany, because his preferred method of killing was biting into his victims' throats, sometimes right through the trachea. He called this his "love bite." He killed at least 24 boys and young men in Hanover between 1918 and 1924. He also stole their possessions and, according to legend, sold the bodies as "mincemeat" on the black market. He eventually confessed, saying that he didn't mean to kill them, but did so in the throes of sexual passion. His deliberate dismemberment of the bodies, however, suggests otherwise. He was executed in 1925.

Dorothea Puente (1929 - 2011) During the 1980s, Puente ran a boarding house for elderly and mentally disabled tenants. She liked to cash their Social Security checks and, if they complained, she murdered them and buried them in the backyard. During her stint as a landlady, she killed as many as nine people and had other people unknowingly dispose of their bodies, including one homeless man who subsequently disappeared. The bodies were later found buried on her property. She was sentenced to life in prison.

Kristen Gilbert (b. 1967) Taking a cue from Jane Toppan, Gilbert also earned the title "Angel of Death" by injecting large doses of epinephrine into patients at the medical center where she worked as a nurse, inducing cardiac arrest. When the emergency happened, she would then resuscitate the patients, saving the day. Four men died from this practice. When the hospital staff grew suspicious of the increase in heart attacks and depletion of epinephrine, she called in a bomb threat to distract investigators. Convicted in 2001, she is currently serving a life sentence.