I've only recently started playing it (as in, last night). I'm aiming to have a completely pacifist run first off :3Can't be done, pacifist can only be achieved after doing a normal one, for more info gogle it.
It can actually, but it's hard because there are a few things you can miss if you're not careful. Once you do qualify for the pacifist run of course, there is some extra stuff you have to go back and do before the final fight in order to lock it in.
Like everyone else I highly recommend playing the game if you haven't. Both looks and preconceived notions are highly misleading there, so you just have to try it.
I think I've played it about three times, just to make sure I got the full experience, and I've watched a couple playthroughs. That said, I did have a bad time... I already basically knew what it would mean, and that I would feel like a terrible person for doing the genocide route, but I heard some things about that run that sounded worthwhile. It took at least 60-70 tries to conquer the final battle, which included switching off with my younger siblings. xD
But yeah, definitely one of my top-10 favorite games - if not #1.