Paul Dano's performance.

I was really taken with it. It was such a muted performance, simmering underneath with emotion like he wanted to explode at times. But kept muted and aloof at times. Like he was fighting internally to keep emotions at bay. I don't believe I've ever seen a character/performance quite like his in this film. Very very realistic. And amazed me. The film and characters are very sad/ troubled people, such is life. And I found it very realistic and sad. Great film, but not for everyone to enjoy.