I think we can draw a finer distinction on "likeable characters" between that that we respect and those that we do not.
In the Godfather, the members of the Corleone family et al all had varying aspects of dislikeableness. However, some we could respect, like Vito looking out after the family, Michael's calculating decisions, and Tom Hagen's prudent skill at achieving legal recourse and influence. While other family members we do not respect, like Connie's sycophant tendencies, Sonny's brashness, and Fredo's distorted sense of importance.
Paul Conroy was a dislikeable pr!ck with no redeeming qualities going into the box or dying with him in the box.
Gimme someone I can sympathize with even at the last bloody gasping second, not someone I'd wanna drill holes so the sand could suffocate him faster.
I guess it's a matter of opinion but I did not find any characters in the Godfather redeeming. I wanted them all to go down, a lot more than Paul Conroy, but that's me.