The first half of the movie is amazing. Great tense buildup with a scary atmosphere.Then the ending was where it fell down.
SPOILERS FROM HERE:
Let me get this straight I don't have a problem with the idea of the ending. The monster actually being Neanderthals was fine, it was more how it was executed that was poor. I got a real sour taste with the ending. The reason being they'd built it up so much that there was a monster in the darkness, to point the point where it could only be a monster in darkness in my mind. Like there was multiple unexplainable things that happened that couldn't have been the Neandarthals. Like them grabbing the kid unless he had super strength and super speed he couldn't have grabbed him picked him up whilst he would've been fighting back and outran the father, It made no sense. Overall 6/10