Abigail Mitchell should have gotten away with it in "Try and Catch Me." It is clearly implied that Edmund murdered her niece.

Paul Galesco in Negative Reaction. I'd of killed that piece of work myself!

Alex Bennedict is a mysterious character. I never wished that he got away with it, but as the movie goes on it seems to be clear that he really loved his wife. The final scene with his wife is kind of touching.

Colonel Rumford... Such a man of honor, and the victim and even the guy he was trying to frame were not exactly the most sympathetic people around.

Brimmer was clearly a flawed man, but he seemed to sincerely admire Columbo. Saw great potential in him right from the beginning. Also his murder was accidental, not excusable of course but he was certainly not trying to harm anyone.

Carsini was a decent man too, but someone already elaborated on this.