Karle Denke murdered and cannibalized at least 42 people, mostly villagers, between 1903 and 1924 in his Münsterberg apartment in then Prussia (pictured). It is thought that he even sold the flesh of his victims at the Breslau (now Wroclaw, Poland) market as pork. A victim was able to escape and later police found cured human flesh in his home. Denke hung himself in his jail cell two days later.

Fritz Haarmann is thought to have sexually assaulted, murdered, mutilated and dismembered at least 24 boys and young men between 1918 and 1924.The full extent of his crimes were revealed after 500 pieces of human bone, some with knife marks, were found by Hanover residents worried about the disappearance of children in the area. Haarmann, who was once a police informant, was beheaded in 1925.

Karl Grossmann killed his victims and sold their meat on the black market and at his hot dog stand. After neighbors heard screaming, police burst into his home to find a dead young woman on his bed. It's unclear how many lives Grossmann took, but he was suspected of dismembering 23 women and involvement in up to 100 missing cases in Berlin. He hanged himself in 1922.

Friedrich Schumann was a locksmith who raped, murdered and stole from 1918 to 1920. After a confrontation with a local forester — whom he shot — Schumann was arrested and charged with the murder of six people and attempted murder of 11 others. He was sentenced to death six times. The night before his execution at aged 28, he admitted to killing 25 people, including his first victim — his cousin.

Paul Ogorzow was convicted of 31 sexual assaults, the murder of eight women and attempted murder of six others in Nazi-era Berlin between 1940 and 1941. Ogorzow worked for the German commuter rail system and would threaten, stab or bludgeon his rape victims before sometimes throwing them off the moving train. He was sentenced to death and beheaded two days later.

In 1946 and 1947, Rudolf Pleil worked as a border guard in the Harz Mountains and illegally trafficked people, mostly women, from East to West Germany. For a while, he had two accomplices who would help trap victims. Pleil was convicted of killing a salesman and nine women but he claimed to have killed 25 people. Sentenced to life in prison in 1950, Pleil committed suicide eight years later.

Joachim Gero Kroll was a serial killer, rapist, child molester and cannibal. Between 1955 and 1976 he murdered up to 14 people, mainly women and young girls. When he was arrested in 1976, human remains were packed in his refrigerator and he was in the process of cooking the arms and hands of a 4-year-old girl he had just killed. Imprisoned for life in 1982, Kroll died of a heart attack in 1991.

Fritz Honka was notorious for killing at least four women between 1970 and 1975. He strangled prostitutes in his apartment and cut up their corpses. Firefighters found hidden body parts in his apartment after a fire broke out while he was gone. Honka was sentenced to 15 years in a psychiatric institution. After his release in 1993, he lived in a retirement home until his death five years later.

Werner Pinzner was a for-hire killer for pimps in Hamburg's red light district. He is thought to have killed between seven and 10 people. Pinzner gained nationwide fame in 1986 when he was brought to the Hamburg police department for interrogation with his wife and lawyer. He suddenly pulled out a gun and shot the investigating prosecutor before turning the gun on his wife and himself.

Marianne Nölle, a nurse from Cologne, killed patients in her care by poisoning them with an anti-psychotic drug between 1984 and 1992. Police believe she actually killed 17 people and attempted a further 18 murders, but she was only convicted of killing seven patients. She has never confessed to any of her crimes. Since 1993, Nölle has been serving a life sentence.

Volker Eckert was a German trucker who murdered at least nine women, most of them between 2001 and 2006. According to police, there were probably four others. His first victim was a classmate whom he strangled aged 15. Most of his victims were prostitutes he picked up across Europe, and he kept trophies like his victims' hair. Eckert hanged himself in his cell during his trial in 2007.

Stephan Letter is a former nurse responsible for the death of at least 29 patients by lethal injection at a Bavarian hospital between 2003 and 2004. Arrested for drug theft, Letter confessed to some of the killings, insisting that he was trying to relieve suffering. He is serving a life sentence and until recently, his acts were described as Germany's worst killing spree since World War II.

Keen to impress colleagues with his life-saving skills, Niels Högel would inject patients with cardiovascular medication to induce heart failure or circulatory collapse. He was convicted of killing two people and was jailed for life in 2015. However, after a multiyear probe, investigators now believe the former nurse was responsible for 100 more deaths, making him Germany's most prolific killer.