"Kill List" is not what I would call a straight-up horror film, but more of a brutal crime-drama that drastically shifts gears mid-way through the third act. That said, it's quite an enjoyable movie.
Two former soldiers-turned hitmen - one being a hair-trigger sadist with an ongoing marital spat and the other being more professional - are hired to wipe out a list of three people given to them by a shady client. Their first mark is a priest, then a kiddie porn operation before they end up balls deeps in a plot hatched by a cult of wacko's dressed as tribesmen.
I wouldn't consider "Kill List" a GREAT film by any means, though it does contain a good amount of carnage and solid performances. One problem I could not overlook was the huge amount of indecipherable dialog. I've seen plenty of UK films, but for some reason I had a very hard time making out what was being said most of the time due to the thick accents. I'm not sure if it was the sound mixing or what, but it's a bit irritating if you don't have a closed captions option. Anyways, as previously mentioned, "Kill List" is basically a dark crime/suspense set-up for about the first hour or so before exploding into a rather intense 'horror' climax including a claustrophobic tunnel chase and ritual sacrifice. The final scene seemed to be lifted from "A Serbian Film" kinda, but was still a pretty satisfying finale. I'd say check out "Kill List" if you like gritty crime films with a "Wicker Man" spin thrown in for a third act.