A whole series of disparate events come to a violent conclusion and dozens of bad guys are killed. That's about as much of a plot summary as you need for a movie like this. Action films can work well with a minimal backstory, and sometimes they work well when the plot gets convoluted. This is one of the latter. A sequel to "The Accountant" from almost a decade ago, it finds Ben Affleck as an autistic but functioning human being with extraordinary financial skills. In the first film he was a savant and an extraordinary killer. He's not really an assassin anymore, but his old skills have not left him and he calls on them along with his estranged brother by John Bernthal, to wreak havoc on a trafficking organization.
If you want the audience to really hate the bad guys, you give them the worst kind of criminal activity to be involved in. In this case it is human trafficking, primarily of illegal immigrant women into prostitution. I don't think it's a spoiler to discover that one of the ways the organizations controls the women, is by imprisoning their children. We don't see it on the screen, but there is little doubt that an economic stream involving the children will eventually be in their future as well. It is by a strange series of coincidences, that the head of the FBI Financial crimes unit gets involved in a case that connects the trafficking group with an assassin.
Of course to fight against assassins, it helps to have a couple of Assassins on your side. That's where Affleck and Bernthal come into play. The FBI chief gets a little squeamish working with killers who don't have the same restrictions of legal Authority on them. Still they end up approaching the case from different directions, and ultimately connecting a dangerous assassin, to the crime ring. There is a bit of a twist in this plot development, I'm not sure it makes a whole lot of sense, but they do try to explain it.
Affleck's character lives in an Airstream trailer, and connects with his financial Empire through a mysterious computer center, filled with children who, like himself, have some Savant abilities. It's been almost 30 years now that filmmakers have been trying to make computer hacking interesting on screen. Programmers, typing in code onto a computer screen, has to be inter-cut with a lot of other activity to make it watchable. The "Accountant 2", does these hacking scenes as well as anybody else has.Although you would not want to know either Affleck or Bernthal's characters in real life, they make a fascinating pair in the movies. Occasionally questions come up concerning morality, but they're never really answered. There is usually some joke that gets them out of a moral quandary. This was a very effective action piece, with a story that was mysterious enough to keep you intrigued for the 90 minutes that the movie runs. Then we get a shootout, multiple deaths of bad guys, and a couple of closing lines suggesting that we'll be back with this crew again.