Edmund Kemper
Kemper was formidable: He was 6'9", weighed over 300 pounds, and had an IQ of 145. His victims included his grandparents, several women, and even his own mother. Authorities believe Kemper murdered 10 people in total, and he reportedly kept some of his victims' heads for days before disposing of them.
I remember this interview. These people remind me of cats that like to play with their prey. Must be born this way. Maybe a cure for them some day.