Horror movies, especially slasher flicks, often leave the identity of the villain unknown for most of the film and this is sometimes a very good thing, since it keeps viewers guessing and, if done right, leads to an entertaining reveal.
At the same time, the device of an unknown villain can be a double-edged sword in that a poor choice of killer, such as someone who couldn't plausibly have done the killings or a random character audiences have no emotional connection to, can undermine or even outright break the entire movie.
It's never a good feeling when one spends an entire horror film waiting for the big reveal only for it to fall entirely flat. Sadly, with these following ten movies, that's just what happened.
10. Identity - Timmy
Identity, a criminally underrated horror movie, depicts ten strangers being hunted down one by one by an unknown murderer at an isolated motel. It features a very memorable plot twist in which it turns out that the characters in the film are actually all separate personalities inside the mind of a killer. It's better than it sounds.
Anyhow, one of the personalities (the killer's murderous personality) is killing all the other personalities and it's revealed at the very end to be Timmy, the personality who was a nine-year-old boy and who appeared to have been murdered earlier on, but had in fact staged his death.
The movie overall works, but Timmy wasn't the best choice for the killer. Having a little boy as the big bad just felt a bit too silly and given that the film is so full of outlandish plot twists, this final twist felt like one too many. Having one of the adult characters as the killer would've been far better, especially since Timmy wasn't one of the film's bigger characters and having a major character as the surprise villain is always better.