My problem with the ending was it didn't tell us if MAx has faced all of his demons. Then again, I'm the guy who went back and emptied several clips in that Mafia boss' kid's face to make sure he wouldn't have an open casket. Serrano was the closest to becoming an effective antagonist, but then they had to go and make him appear all sympathetic during his last said: A lot of the villains you barely ever get to see really, and they only appear for a few minutes at a time.
All of the different organisations made it a little tough to follow, and while Victor being a bad guy was highly predictable, I never got to see him doing much in the way of any nefarious deeds so I never felt the surge of anticipation in putting a bullet between his eyes like I did for say Edgar Ross or Dimitri Rascalov.
I was never all too invested in the story anyway, so it blew it over without me caring too much. This was basically my train of thought as well. Him not killing Victor at the end was him sort of proving to himself that he didn't have to.
The whole game desensitizes you to killing. I don't really like spelling out what stories mean to me, or, like, over-analyzing video games, but I think that was kind of the point.