I find this poster upsetting in a very visceral way. This closeup image of a crying Naomi Watts just has a certain rawness that makes it disturbing in a way that I don’t often find movie posters to be. And even the placement of the title and credits helps to make the poster feel slightly wrong in a upsetting way. It makes the poster seem less like just another movie poster.
Of course, I imagine that is exactly the type of reaction they were going for. The New York Times had an interesting story about Michael Haneke, director and writer of Funny Games, which highlighted how much he likes to challenge the audience and to force them to consider why they feel like they feel about certain things. In particular he likes to take on the general attitude towards violence in the typical Hollywood film. So his films are unlikely to offer a comfortable experience to the audience, and I like that the poster embraces that, instead of trying to make the film look like a more typical and easy to watch thriller.
As an aside, this poster is for the remake of Funny Games, which is very close to being a shot by shot remake of the original, which was also directed and written by Haneke. However, the original poster was very different.