This is a chilling subject. The highest confirmed victim count of any serial killer ever is that of the late and not lamented Dr. Harold Shipman, nicknamed "Dr. Death". He killed at least 215 of his patients:

http://news.bbc.co.uk/1/hi/uk/2138888.stm

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"Some people complain about the system. The system is not good, so they can't do anything. It's an excuse. Freedom is in your heart." (Jin Xing)