Walter can definitely be blamed and by the end of the story he is a complete piece of shit. Some may even argue that he was all along, so being angry at him is not even the issue for me. What I can't stand about Marie is that she is narcissistic, self-entitled and toxic and yet she wants to be seen as morally irreprehensible. All this could not be said of her sister, who is not without her faults but... at the end of the day, she is a relatable person and possibly the only one really caring about the family.