I agree with LK...I don't think Stalin and Hitler were "great" leaders. They used their brain and charisma for evil acts of hatred in its purist form. These two are by no means role models for aspiring leaders to be.
Since the Holocaust seems to be the focus my pick would be Joseph Mengele.
Donate to UBBDev today to help aid in Operational, Server and Script Maintenance, and Development costs.
Please also see our parent organization VNC Web Services if you're in the need of a new UBB.threads Install or Upgrade, Site/Server Migrations, or Security and Coding Services.