Easily Kubrick's most overtly humanist work. You definitely get a sense of the anger, distrust, and resentment he has for institutions--like we see in Dr. Strangelove, A Clockwork Orange, and Full Metal Jacket. And talk about a genuinely affecting Kirk Douglas performance, to boot. Anyway, a solid first near-great from Kubrick.
Jesus H. Christ. I vaguely remember this from when it came out, but seeing it now, this time in a theater? The only other documentary this decade that feels nearly as complicated is Minding the Gap, and that looks like babytown frolics next to The Act of Killing. Easily one of the great works of non-fiction filmmaking of all time. Maybe even top five.