A Dragonfly for Each Corpse
Una libélula para cada muerto (original)
A Milan police inspector investigates a string of killings of underworld figures, each linked by an ornamental dragonfly left on the victim's body.
Starring Paul Naschy, María Kosty, Erika Blanc, Ángel Aranda, Ricardo Merino, Susana Mayo, Eduardo Calvo, Mariano Vidal Molina, José Canalejas, María Vidal
Watch "A Dragonfly for Each Corpse" on Tubi TV released in 1973. It's a crime and mystery movie, and has a rating of 5.7 out of 10 from Imdb which is fairly okay for this kind of movie, and is currently available to watch for free.