Daniel Camargo Barbosa
In the 70’s and 80’s, Barbosa was busy. It’s estimated that he had raped and killed as man as 300 young women, and left their bodies behind to be found. Some of his victims were as young as 9 years old.
When he was finally caught, he was carrying a bag of body parts and bloody clothes, and caught the eye of the police because he was acting suspiciously. He ended up confessing to half the estimated number of murders and took the police around to the sites where the murders happened.
While serving his 25 sentence in 1994, he was attacked and killed a fellow inmates. That’s karma.
You forgot Harold Shipman, probably the world's most prolific serial killer and a doctor.