10. Harold Shipman
This unassuming doctor is often referred to as one of the most prolific serial killers in the world. He was an English General Practitioner who had a penchant for murdering the patients in his care, from 1995 to 1998 he murdered fifteen patients by giving them lethal doses of diamorphine (heroin).
In 1998, concerns were expressed to the coroner about the high mortality rate among Shipman's patients, this was investigated but ultimately dropped. After this Shipman continued his practice until the death of Kathleen Grundy. Grundy's daughter was suspicious of the will produced as it left everything to Shipman rather than the family, upon investigation the body was exhumed and found to contain traces of diamorphine.
This sparked an inquiry, known as The Shipman Inquiry, into his behaviour. It was discovered that many other patients had passed away in his care, he had then signed their death certificate and forged medical records to suggest they were in poor health.
He is the only medical practitioner ever to be convicted of murdering his own patients. Shipman later hanged himself while in prison sparking an inquest into prisoners mental health. In total, 459 patients died in his care from 1971 to 1998, however, we will never know how many of these were from illness or from Shipman's hand.