That scene was terrific, at the beginning when Kim Go Eun was performing the exorcism or whatever it's called, that was intense, literally got goosebumps. The music and everything was so intense, I watched that part thrice. I liked the movie a lot. And genuinely can't understand the hate people have for it. First they watch it because of hype thinking they'd look cool if they knew about it, but get disappointed if it doesn't match their interest. No body forced them to watch this movie, you watch it on your own consequences and then blame the director, writer etc. They don't understand that this movie might not be your cup of tea (but you'll find one soon, so stop bitching about it). You're supposed to appreciate their work and efforts.
I liked the movie, as a person who doesn't like horror, it was good for a beginner, since it didn't had any scary or horror scenes, (and bloody, stabbing, extreme violence: I'm used to those because I love those type of dramas.)