Who is the most brutal serial killer in history?

There are several who would be worthy of the title. Those few include BTK, the Green River Killer, and Jeffrey Dahmer. The most notorious however, would most likely be Jack the Ripper, mainly because he was never caught. If we go by numbers of victims Christman Gniperdoliga killed 964 men between the years 1568-1581 after robbing them in the Roman Empire area