Worst serial killer(s)?

[Harry D]

I'd have to go with the 'Dnepropetrovsk Maniacs' as some of the most heinous, particularly in modern times. Not only did they commit despicable attacks on innocent people (one of whom was a pregnant lady), but they were also lazy. They indiscriminately targeted men, women, and children, rich or poor. Whoever they could get their depraved hands on.

[Harry D]

Which serial killers do you consider the most nefarious, and where does our very own Ripper rank among them?