It has been a while since I saw this movie the first time, but watched it again recently on Netflix with the family. First and best thing it has going for it...villains you don't care about. Seriously, since Nazis we've had a real shortage of villains you can find in the real world who are basically just so evil that you don't care what physical violence is done to them. Sex Trafficers are a good addition to that list though.
The film goes through an excellent set up, with the daughter willfully ignoring her concerned father's legitimate security concerns, which also end up saving her life in a fantastic scene (seen in the trailer so not a spoiler) where she is hiding under the bed and has to reveal details of her kidnappers in only a few seconds.
And then we see Liam Nielson get to work. He's not batman. He is absolutely lethal in combat, but it is still at the believable gritty real world level. There are no absolutely over the top vehicle scenes like you see in a lot of movies in this genre, and while the film does push the envolope (hard) it stays (in my opinion) in the 'this could theoretically happen in the real world' scenario, including why people like the slavers are able to get away with a lot of what they do.
Its an action thriller but Liam's performance is so good that you are emotionally connected to him as well. You can feel his absolute torment as his daughter is suffering, as he helps the other victims that he manages to find or rescue along the way and has concerns for them as well. He is a one man force of nature and (again from the trailer) the bit where he threatens the guys who take his daughter...and delivers on that threat are excellent.
There is, I should warn, torture in this. I'm firmly against torture, but I understand that it is used sometimes. From an artistic stand point, I would have found it less believable if he hadn't tortured when he felt he must. They're not portraying him as a saint, but a 'flawed but good man' which comes across in this. Conversely, he is never sadistic or truly vengeful, just ruthlessly efficient and utterly without mercy at those who have taken his daughter.
It is, to be blunt, an absolutely fantastic movie and if this kind of thing interests you, its a must see in the thriller/action genre.