In how many episodes with a pretty unpleasant victim do you sympathize with the killer without sympathizing with the victim any less? In my case it often includes victims you aren't really EXPECTED to like that much, or maybe at all -

Adrian and Ric Carsini (I can never help liking those stereotyped jet-setter characters, especially if you're, again, expected not to. Which describes Ric in his one scene. Besides, just as he says, he knows how to ENJOY that money. But then, so does Adrian in his way, it just isn't as obvious.)

When it comes to would-be victims who survive, Nora Chandler and Jerry Parks. (I know you aren't supposed to like Jerry, but Mel Ferrer really causes me to. Besides, as I said a while back, he seems genuinely shook up over Jean in that restaurant scene.

Elliott Markham and Beau Williams. I don't know how much you're really invited to dislike Beau, but he does comes across as unpleasant (especially since Elliott isn't just plain TAKING his money). But to the degree you might be invited to, I really can't. Elliott has this dream of creating something - which is admirable - but when Beau says holding on to his money means more to him than some incredible building with his name, I immediately sympathize with that too.

I'm not sure if this fits the topic perfectly, as I don't really think either character is ultimately sympathetic at all, but "Candidate For Crime" is an episode that comes to mind.
Both Nelson and Harry are completely reprehensible, but if I put myself in Nelson's position I can certainly sympathize with the pressure he's under from Harry, if not his actual sense of values.
With Harry, while I don't sympathize with his selfish motives for ending Nelson's affair or his general manner, I somewhat sadistically relish the thought that someone as arrogant and self-centered as Nelson has had to deal with a guy like Harry for so long (of course, after Harry's murder, Columbo sort of slips into the role of Nelson's gadfly, thankfully with much purer intentions in breaking Nelson down than Harry ever had).