Just don't commit some injustice, such as murdering his cellmate buddy, or intimidating your accountant customers at their farm, or placing his A-list would-be girlfriend Anna Kendrick on your hit list. Because, then, Ben Affleck transforms from the deadpan Rain Man into Jason Bourne, and will slaughter all your hitmen and kill you, no matter how many of them there are, and even if they know you are coming.
Because it is a movie, and we all expect to see John Lithgow take a bullet to pay for his own transformation, from affable and altruistic into a gangster with his own private dirty dozen.
True to genre, there are plot twists, in fact three of them. The first two are merely implausible, and the second is ridiculous. More on this subject later.
How others will see it. The Accountant is a thriller stocked with well-known actors, with the look-and-feel of his buddy Matt Damons' Bourne films.
Bourne, if you recall, isn't much with the emotions either, and all of the people he kills are bad guys who have it coming, or make the mistake of working for bad guys, which, in an action movie, is practically the same thing.
The Accountant has more or less been ignored by the film festivals. It did make triple its budget in worldwide theatrical gross, and it does have a respectable 100K user votes at imdb.com. At that website, the user votes are reasonably high at 7.4 out of 10. Women actually grade it slightly higher than do men, perhaps because they like seeing murderers "taste some of their own medicine", and because Anna Kendrick survives without paying for it with the usually requisite sex scene.
It is true, though, that the Top 1000 voters, who presumably have seen many high budget thrillers, vote it lower at 6.5 out of 10. Perhaps they can see the numbers behind the paint (by which I mean that they can spot the paint-by-numbers formula).
But most viewers don't care that the movie looks like many they have seen before, at least as far back as Die Hard three decades ago, if not that Bruce Lee movie where he takes out Kareem Abdul-Jabbar along with the rest of the cast. Instead, they are intrigued that the hero can audit the books in a day better than a CPA team could do in a month, plus save the Pauline in Peril from a gang of ruthless, cynical, and easily murdered henchmen.
How I felt about it. Plot twists are important to thrillers. Ideally, they take after The Sixth Sense, in that they merely illuminate what has happened earlier, instead of channeling Fight Club, and make a joke out of the prior scenes. It's no surprise that John Lithgow turns out to be the evil Mr. Burns. That became obvious once his sister was shot. Not only is it predictable, it is also incredulous. I can believe that Lithgow would cook the books. I can't believe he becomes the stereotype of a cinematic corporate gangster.
Ben Affleck's morality is also hard to figure. Kill someone he likes, or try to, and he will wipe out your entire organization to get to you and off you. Yet he's willing to work for the worst criminal enterprises in the world, whom are likely to be killing plenty of people, though not Affleck's cellmate buddy. Does Affleck object to the principal, or only the exception?
As for Ben Affleck's brother. Couldn't he have worked for the U.S. government, such as a Navy Seal, instead of taking the money of any mass-murdering despot who will pay his salary. And if he does such a thing, why is Affleck willing to overlook it, simply because Jon Bernthal is his brother.
I won't vent too much about the Rain Man or A Beautiful Mind syndrome, in which someone in a movie with crippling psychological maladies must also have spectacular mathematical abilities. But I will say that a grown woman who acts like a frenzied gorilla is difficult to reconcile with a computer presence of a sophisticated problem-solver. But her morality is suspect also, since she enables a man who works for gangsters when he isn't killing them.