In my opinion this game is very, violent and sadistic but frankly as Ohm said it doesn't break any boundaries that haven't been broken. It takes itself so not seriously it intentionally makes a laugh about it. It's a stealth parody, one that had effort put into it. I don't think this game is too violent as much, much worse violence happens in real life. At least when you the killer do go out of your way to kill the victims you know you are doing something horrible. This game doesn't mask your killing people as something 'cool' or heroic, nor does it hide behind character development to justify it. It's pure unmitigated intentional horribleness and an honest one at that.
Look at Blood Meridian: now that is a sadistic book, one that doesn't romantacize its violence. It's pornographic in its depiction of it unlike say a Game of Thrones whose violence is cartoonish.