2 more from Criminal Minds
The guy from Seinfeld that played George did a wonderful scary job.
This comedic actress played a serial killer Hitwoman that tortured Dr. Spencer Reid psychologically over several episodes.
Yeah, the Boston Reaper was legitimately scary. He was evil in a way that almost defied reason. There were several UnSubs on the show who had tragic enough back stories that you almost felt a sense of understanding, not that you agreed with what they did but you could at least recognize a twisted sense of justification in their mind. This guy definitely had a tragic enough childhood but his actions were too extreme.