Movie blames the mom
Did anyone else think that this movie implies that Kevin turned out the way he did because of his mom's fault? The movie shows how she's extremely apprehensive about having him (i.e. losing her freedom, the pre-Kevin tomato scene is the happiest we ever see her). Even in the scene where she's giving birth, she's apprehensive about bringing him out into the world.
So once we get into Kevin's infancy part of the movie, the scenes get juxtaposed between Ava not wanting him there (even when he says, you don't like me, you're just used to me, she doesn't correct him) and him acting out. Then when he starts showing violent behavior in his teenage years, the audience is supposed to go, well of course, look at the mother he has...
I've seen other people say that the movie shows how, while the dad is oblivious, she's the only one who perceives his true nature . But I really think the movie doesn't support that theory. I think it's portraying quite the opposite. I think the movie implies she caused it.