Pitera enjoyed killing people, I don't think Demeo 'enjoyed' it. Demeo was broken for a period when he discovered he killed an innocent boy.
One guy in Demeo's crew who really creeps me out is Chris Rosenberg. Some say he looks a bit goofy in his known picture, but I think he has that Last House On The Left/Texas Chainsaw Massacte-aura about him lol. He also ruthlessly butchered a couple of Colombians and a Cuban. Which, in those days, wasn't really a good career move.