These lists are always the same, most famous but never the worst. The serial killer with the highest amount of victims is actually from Columbia, Luis Garavito he's called. He has 100+ proven victims but the real number could be 300+. Obviously Harold Shipman tops this with over 200 proven, but because he's a medical professional and allowed to murder in plain site he is usually in a list of his own.
There's actually no Americans in the top 10 when it comes to victims surprisingly , they are all from South America and Asia