It almost feels to me like I already reviewed this film considering the similarities it holds to fellow British horror movie "Severance". But there are subtle differences. Mainly the fact that this movie isn't a comedy at all, and the story revolves more around revenge driven retaliation than a bunch of random slayings by war sickened ex-military individuals (although the killer in this picture actually is ex-military).
The story is entertaining (albeit not all that original), that going along with the interesting characters, who happen to be a cutthroat group of youth prison inmates sent to a remote island to "learn a lesson" or something of the sort, gave me pause to stay tuned. For the most part it is a well acted affair, with good plot twists and unpredictable behavior keeping you guessing throughout.
But where this movie truly succeeds is with the violence(which also smells of "Severance") but is totally brutal and masterfully executed. Canine disembowelment, ultra violent beheadings, various dismemberment and stabbings.... the usual fodder just very well done.
So in going with the assumption you haven't seen "Severance" (which I found out actually came out in the U.K. within two weeks of this film) I would recommend this movie highly to a very wide audience, and if you have seen it....watch it anyways it's good.
7/10 detached retinas