John Nelson

John Nelson is a serial killer that appears in Criminal Minds as the main antagonist of the episode God Complex in season Eight.

Biography
John Nelson was a grave digger who was married to his wife Linda who suffered from a form of hypoplasia, that she was born with the leg missing only the knee and being forced to use the prostheses as result to walk. John left the funeral home job and had and idea of implanting a leg of another person in his wife, he also got the medical equipment to mount in his house in his garage. He then started with experiments first on mice and then on humans his first victim was Richard Hubbel who after the experiment he was found dead in fice days later.

John later kidnaps Tony Anders and takes him to his garage. John then removes his leg but can not do the surgery., Tony then runs away without his leg. Tony was later called by the BAU for questioning in the case. Then John kidnaps Carl Timmons and removes his leg and puts Tony's leg on him and was released and soon died on arrival at the hospital. John also kidnaps two woman, Maria Rodriguez and Donna Sullivan does the surgery in the two and exchanges his leg that Maria then has Donna's a leg and while Donna has Maria's leg. While Marie died from the surgery, Donna was released because of John's threat. Donna then disengages from her moonrings and threatening, Linda with a scalpel but John fools her and puts her in a sedation. Linda then realizes what John has injured. BAU arrives and John threatens to drug again plus Reid manages to convince him to be deliver, John is later arrested for his crimes while Linda with sob exclaim her name.

Then John's modus operandis was copied by John Curtis as revenge against the BAU and Alex.