"Negative Reaction" is the most carefully
prepared murder, and he almost got away with it.
Columbo had to trick him to get the goods on him.
Even though Galesko made mistakes like forgetting
about the scraps of paper, none of this was
enough to incriminate him.

"Troubled Waters" is also well plotted by the
murderer, although I think it was dumb to plant
the gun on Lloyd Harrington. If Columbo hadn't
found the feather, there wouldn't have been anything
pointing to Hayden Danziger.

"A Friend In Deed" tops my list too. Always has.