In the movie, after discovering that Nick is cheating on her, Amy frames Nick for her murder. But on a deeper level, Amy sets him up for failing. For not living up to her expectations for him. For no longer being the bright young guy that she agreed to marry. She punishes him for being a disappointment and for daring not to meet her at her level. In real life, women actually get murdered for much less. And to me, that's what makes Amy's fabricated story so believable to the people around her. The situation is not just totally plausible, but likely, because we hear about the repercussions of stories like the one that Amy concocted every day.
On the face of it, Gone Girl is a misogynist's wet dream. It validates every bullshit MRA fear that women are out to destroy men. After all, Amy frames ex-boyfriends for rape as a matter of course, meticulously frames her husband for murder, murders a different ex-boyfriend during sex, for the crime of helping her escape her "abusive husband" and being a little too possessive, and then traps her husband in their loveless marriage by stealing his sperm to become pregnant. It is a literal laundry list of things that convince men that feminism at its core is simply a "misandrist revenge fantasy."
But in truth, Amy simply took her frustrations to the same "logical" conclusion that men get to every day in the real world. Instead of just leaving Nick, she transposes all her frustrations onto him and then punishes him for them. But how is that any different from the men who beat their wives because they're frustrated with their own unemployment? Or hide their assets so they can run off with the new girlfriend and leave their wife destitute? Or the ones who kill their wives for cheating, or God forbid, "dressing too sexy" or even looking at another man? In Gone Girl, Amy and Nick's positions are simply reversed from the traditional roles of aggressor and victim.