The interrogation of Williams by Detective Smyth is astounding in its subtlety and effectiveness.
I've read that he undertook extensive preparations for it, consulting with psychiatrists and criminal profilers from both Canada and the United States.
The whole thing was sequenced very carefully, and he "walked" Williams from respected Air Force commander to serial killer in a series of small steps, each of which offered no way to back up.
The Markoff interview is just as good in my opinion, except that Markoff pulled the plug and asked for a lawyer instead of giving an explicit confession.
However, before he asked for a lawyer, he made it obvious that he was the murderer.
Detective Smyth was able to use Russell Williams' own sense of honor and responsibility to extract a full confession and a detailed description of each murder before the interview ended.
I agree Craigslist Markoff was interesting as well....but i think watching Israel Keyes was a cut above that for the nature of how he covered and planned his killings and was so manipulative in the interrogations... .........any others you found interesting please do refer as I do enjoy watching the interesting ones.