In the ending credits sequence of Murder Of A Rock Star, Columbo is driving down the highway with the top of his car down, singing along to the victim's hit song that's been played earlier in the episode. The camera cuts down to show a brand new battery-operated boombox, purchased from Dhoti's Discount, which ended a small subplot from early in the movie. One of the victim's CDs is also sitting propped up against the boombox. Columbo picks up the cover, looks at it and smiles, almost as if he was telling her that she could rest as her killer was caught.
The episode 'Any Old Port in A Storm' when Columbo allows Donald Pleasance's vineyard owner a final drink (and makes an effort to chose a wine that Columbo knows he will enjoy) before taking him off to sign his confession.
The season five premiere "Forgotten Lady." It's the one time when Columbo doesn't arrest the perpetrator, who is terminally ill. Her devoted partner confesses in her stead, in hopes of delaying the inevitable long enough for her to die in peace.
"By Dawn's Early Light" had one between Columbo and Col. Rumford. Col. Rumford expresses a deep remorse at the state of the world and its need for police and the military, and hopes that one day he could just retire, the world no longer fighting, and that Columbo could also retire when the world finally becomes peaceful enough to have no further need of the police. It actually made the killer feel even more sympathetic, as he only did what he did because he felt that turning the military academy into a junior college would be a severe blow to the military, which he felt was an unfortunate necessity but one that should be preserved as long as it was needed.
At the end of the episode Swan Song, Columbo catches the killer (played by Johnny Cash) as he tries to remove evidence from the crime scene way up in the mountains. The murderer comments that he's amazed that Columbo would risk coming up to the middle of nowhere with a man he knows is a murderer. Columbo, in response, turns on one of the man's songs on the radio and tells him "Anyone who can sing like that couldn't be a murderer for long."