Helen Shaver as Vivian Dimitri in 'Rest In Peace, Mrs Columbo', is excellent as this slightly deranged but beautiful killer. The character is a fine balance of madness, sexuality and cunning; and Helen Shaver does a great job of portraying her. This is an under-rated episode from season 9, possibly because of the clumsy and unimaginative title.

Hands down it's Trish Vandevere as Kay Freestone in Make Me a Perfect Murder. I thought she played the part so well. She showed the stress well, portrayed the tough corporate executive well all the while also portraying a loyal friend, was beautiful, her voice was alluring, and her performance resulted in one of my favourite episodes (aside from the filler scene of Columbo playing in the projection booth that everyone has been referencing as I always thought that was useless as well).

If I had to decide, it would probably be Lee Grant as Leslie Williams. Partly because of how great she is in the role, and partly for "biased" reasons - she's the only one (at least in the original series) who works as a genuine "femme fatale" for me. Any given look she gives and any given line she says is just plain hot.

I go with Kay also. The actress played her very well. Considering her possible motives, none of which really gets us sympathetic (discussed on this forum), we can feel a wide range of emotions about her.

Another one for me is Nora Chandler. It's an easy expression to throw around, but Anne Baxter was a "Golden Age of Hollywood" actress, and she gave that kind of quality to Nora Chandler the actress.

These are big SPOILERS for anyone who hasn't seen it.

She manages to make you sympathize with her in spite of what you find out along the way about her murdering her husband, her deliberately (not accidentally) killing Jean, and her trying to kill Jerry. At least, to me it does.

I have to go with Jon Bird in this one. RIP Mrs. Columbo was under rated but was a great episode. Her character was portrayed perfectly.