Given that The Foreigner stars 
Pierce "best James Bond since Sean Connery" Brosnan and 
THE Jackie "most brilliant and funniest martial artist to ever live" Chan, about a dad with special abilities beating up bad guys, there have been so many speculative anticipations of what The Foreigner might be that I think it best to start off with what The Foreigner is NOT.
The Foreigner is not comedy Kung-fu master versus James Bond. 
Nor is The Foreigner a version of Taken-Chan style.
The Foreigner IS a movie which proves that Pierce Brosnan and Jackie Chan are not just movie stars.
I remember the first time I ever saw Jackie Chan. B.C. (Before children) when we actually had time to kill, my husband would flip through channels and occasionally watch a kung fu movie. I found them dull but would sit next to him and either read a book or doze off. 
But then one day he found a movie which featured a guy using martial arts and beating up bad guys…with a LADDER! Who fights with a LADDER!? Of course it was Jackie Chan. The fluidity with which he fought, the cleverness with which he parried blows and attacked his foes were a pleasure to watch. AND he was FUNNY! 
Watching Jackie Chan fight was the martial arts equivalent of watching Gene Kelly dance!
I have been a big fan of Pierce Brosnan for decades. First saw him in the TV show Remington Steele. In this clever old TV show Brosnan plays a con man who impersonates the head of a private detective agency actually owned by a woman. Her business had not been going anywhere because people wanted to trust a male detective. So she invented a masculine boss and Brosnan's character, in a North by Northwest homage, accidentally becomes the flesh and blood front man. Brosnan's Steele was, at the same time, both suave and adorably bumbling, seeing every case as some version of an old classic film. 
Then eight years after the close of the show, when FINALLY given the shot at James Bond, Brosnan ramped up the suave but kept just a touch of the cheek with him, making Brosnan's the best Bond next to Connery they ever had.
…………………..The Foreigner features NONE of the above – nothing of the simpler and lighter personalities we have come to associate with either Brosnan or Chan are in evidence in The Foreigner. 
The Foreigner instead showcases Brosnan's and Chan's talents as ACTORS. Both, to their admirable credit, play strongly against the type we have come to expect and love. 
Chan plays Quan Minh, a father devastated by the loss of his only surviving daughter to an IRA bomb in London. Shuffling humbly from police station to political representative, he personifies an almost stereotype Chinese man. Without giving away anything you wouldn't know from the trailers, it is not long before grief and frustration peels away the onion thin layers that hide the dangerous man he has hidden beneath this carefully cultivated, easy to underestimate, persona.
Brosnan, for his part, plays Liam Hennessy, a weasely slick Irish Deputy Minister who is also both more and less than he first appears. A political animal, Hennessy superficially sympathizes with Chan's character but clearly has his own agenda forefront in his mind and plans.
In the beginning, we watch Chan as his catastrophic loss seems to gut him.
Then we follow him as this emptying out process becomes a metamorphosis. 
Meanwhile, the writer, in a fascinating twist, carves out the background with Brosnan's Hennessy, which explains how this collateral damage came to be. We see a bigger more complex picture through the eyes of the innocent bystander, Minh, who will stop at nothing to get justice for his daughter. The explanation of the intrigue which casually took Minh's daughter's life takes on a life of its own so that we end up with two movies in one. The two stories begin like strands from separate balls of yarn, but become knitted inextricably together in an unexpected and fascinating pattern.
This is not to say that Chan doesn't kick some serious booty – because he does. As my husband is wont to say – they should have never have left him with nothing to lose. And one of the many applaud worth aspects of The Foreigner is that the story does not attempt to turn Chan's Minh into a super hero. Minh's age is even mentioned several times, as in (paraphrasing) "How can we be getting our a***es handed to us by a 60 year old man!"
And Chan, the actor, doesn't hide his age either. 
When Minh takes on two 35 year old men in their prime, it takes its toll on Chan's character, as, I imagine it really did on his now 63 year old body in a realistic way.
Over the years Jackie Chan has let it be known how dangerous his stunts were. 
Chan always was one for letting the audience, especially the kids in the crowd, understand what he does has a price. I always found it laudable that he would make a point of demonstrating in the end credit sequences of his lighter films the bloopers wherein he incurred obvious injuries. He wanted to be sure others knew: when you try to run up a wall and flip over or slide through a small opening or jump kick or slid down a 5 story pole – things happen even to professionals and they get hurt. 
Chan has broken almost as many bones as has the daredevil motorcyclist 
Evil Knievel. OK that may be an exaggeration inasmuch as Knievel holds the world record for the most bones broken by a surviving human being at 433. But Chan has had broken bones, concussions, a slash with an unexpectedly unblunted sword, dislocated cheek bone, sternum, and pelvis (I didn't even know you could DO that!), and his thighs crushed between two cars. 
Chan even has a hole in his skull from a misadventure jumping to a tree in Armour of God. But Chan still is a pleasure to watch, performing martial arts with his signature balletic grace despite his age and previous injuries. 
Chan's acrobatic martial arts in a fight scene is as much a thing of beauty as watching Mikhail Baryshnikov performing a grand jete .
The story of The Foreigner is fascinating and both of these men deserve big kudos for gutsy performances quite different from the meat and potatoes style most people have come to expect. And they do it well.
I have a friend, Stuart White, a retired journalist, who covered the appalling violence of what the Irish called "The Troubles" – that period of time when the Irish and English were constantly and mortally at each others throats – when terrorist attacks became so horribly prevalent that public trash cans vanished as too convenient for depositing bombs. 
Stuart wrote a brilliant book about an IRA terrorist called Shamrock Boy which was turned into a screenplay called
Crossmaglen now in pre-production. While watching The Foreigner it felt like the same world, so from my limited perspective I can say The Foreigner came across to me with the power of tragic authenticity.
Go enter the dark labyrinthian world of The Foreigner, then come back with a new appreciation for the talents of the men we previously knew, respectively, as Pierce "Remington Steele" Brosnan and the comic martial arts master Jackie Chan.
There is realistic violence and some rough language and sexuality from the terrorists. And the human assault which begins the story is terrifying. So mid to late teens would be my minimum age and then only with parental attendance.