One tidbit that stands out to us in all the Last of Us: Part II previews is this idea that human enemies are more, well, humanised. A group of hostile folks will all likely know each other, and are probably trying to protect friends and family.
This won't mean an awful lot for gameplay, but hearing enemies calling out in horror when you kill their companions sounds pretty harrowing. If you've watched any of the recent gameplay footage, you'll probably have seen this in action. It adds a disturbing new wrinkle to combat; your enemies are mourning that man you just murdered, but would sparing him have made things more difficult for you?
These morally ambiguous details sound very The Last of Us -- we can't wait to play it for ourselves.