Re: Killers you like when you aren't supposed to, and vice versa.
For me it was:
Tommy Brown - How can you not like Johnny Cash and his music? If the part had been played by anyone else, I would've despised him for killing the innocent girl.
Abigail Mitchell - Just a sweet, loveable little old lady exacting sweet, deserved revenge on the death of her only daughter. Eye-for-an-eye, I'm OK with that.
Adrian Carsini - This was one of the first Columbo episodes I ever watched, and the first one I saw where Columbo seemed to genuinely befriend the suspect. Poor Adrian!