Ma has all the trappings of yet another Blumhouse Productions low-budget treat, except for the pedigree of its cast. Octavia Spencer is an Oscar winner. Fellow Oscar-winner Allison Janney (the Michael Caine to Taylor's Christopher Nolan -- she's in all of his movies) as a veterinarian has maybe three lines in total, all of them barking at Ma to hurry up and shave that dog. Fast & Furious villain and live-action Gaston Luke Evans has a bit part as one of the kids' dads, who also gets the movie's most gruesome death. This basically means that all the performances in it are wonderful -- Spencer's dead eyes and small stature make her an extraordinarily chilling villain -- if somewhat distracting. Janney doesn't even get a gross death scene!
The most troubling reveal in Ma isn't when she finally goes full psycho on all those kids, but what comes before, when the abuse she suffered as a teen herself finally comes to the fore. When she was in high school, a popular group of kids, including the boy she had a crush on (Luke Evans' character), banded together to come up with a special form of humiliation: They would tempt her into a janitor's closet, making her believe she was about to give oral sex to her crush when in reality it was a completely different boy, and they'd wait outside the door to surprise her when she was done.
The best horror-comedies usually have a switch somewhere in the story that, when flipped, brings a more sober sense of reality to the proceedings, but this is nearly too much. Seeing what happened to her at the hands of her classmates almost makes her too sympathetic to root against, so the movie throws in some Munchausen by proxy to keep her firmly in the villain camp. (Her wheelchair-bound young daughter, revealed to be her daughter halfway through the film, is drugged and kept prisoner in the house upstairs, while all her other classmates party in Ma's basement.) Yes, she's suffered deeply, but look, she's still horrible because she's punishing an innocent child.
The violence, when Ma finally gets around to it, is particularly horrible, which seems at odds with the altogether ridiculous and silly tone the movie strikes for about 90% of its runtime. Taylor can't find his thesis, which is ultimately the thing that keeps his movie just shy of greatness. He's already fielded questions about his movie's odd ignorance of its racial undertones (at one point, Ma paints another black character's face white, saying, "There's only room for one of us"), insisting that that was never part of its design. Octavia Spencer just happens to be the lead. Because Taylor's not about to delve into any deeper issues here, Ma is fun, it's shocking, but it's also weirdly forgettable, which is not something I thought I'd say about a movie with a flash of nearly an entire penis, a scene where a character gets her mouth sewn shut, and another where someone's abs are sizzled by a white-hot clothing iron.