For most who saw it, though, none had more impact than The Act of Killing, Joshua Oppenheimer's disturbing and surreal documentary featuring a group of North Sumatran mass murderers and thugs.
Executive-produced by Werner Herzog and Errol Morris, it curls itself around your brain and guts, making you gasp in queasy, mind-shattering disbelief as you become immersed in the grisly details of Indonesia's blood-soaked 1960s and the personal torment of a man slowly unravelling as he struggles to come to terms with his brutal actions.
This wasn't the film's first festival outing. However, Berlin, where The Act of Killing won the audience award, arguably provided the most resonant setting because of the stark contrast between the ways Germany and Indonesia have responded to catastrophic events that have scarred their national psyches.
Walking around Berlin, it is impossible to escape the triple spectres of Hitler, Nazism and the Holocaust; they haunt the city in landmarks, museums and memorials that bear witness to Germany's descent into barbarism under National Socialism.
In Indonesia, conversely, it has been almost taboo to talk about the more than a million people murdered in anti-communist purges throughout Indonesia in 1965-66. "That fact has long been a public secret, a sensitive issue that has been erased from history lessons in Indonesian schools," Farah Wardani commented in The Jakarta Globe recently, referring to the slaughter that formed the backdrop to military strongman Suharto's rise to power and a 30-year hold on the presidency.
Many of the dead - unionists, intellectuals, landless farmers, members of the country's ethnic Chinese community - lie buried in mass graves. Meanwhile, their killers live as free men, hailed as heroes by political leaders. No one has been put on trial for crimes against humanity. No one lives in fear of losing their liberty for their part in mass killings.
The country is no longer a dictatorship - Suharto resigned in 1998 and died a decade later - but "much more has stayed the same than has changed", claims Oppenheimer when we meet in the Berlinale Palast during the festival. The Act of Killing, therefore, "emphasises continuity", he says, "because Indonesia is a country where the military is still overwhelmingly powerful; where the government and big Western corporations use thugs to enforce oppressive labour conditions or to seize people's land or to break strikes; and where there's still political censorship".
When the filmmaker tried to explore the truth about what happened in 1965 through the experiences of survivors in the plantation belt outside Medan, the capital of North Sumatra, he found: "They were too scared to say what had happened to them because the killers were living all around them." Police threatened the filmmakers with arrest, while plantation bosses and civic leaders regularly found ways to interrupt shooting. Eventually, the survivors asked Oppenheimer: "Why don't you film the killers?" Suddenly, "all the doors flew open". Whereas his original subjects had feared reprisals, the men who'd helped bathe Indonesia in blood were eager to talk about their achievements.
"The first killer I filmed, I was astonished by the boasting," he says. "I thought, 'Here is a very important story about impunity, unless he's unique.' I said, 'Can you introduce me to other members of your death squad, and to other death squads?' " The surprising result was that Oppenheimer met every killer he could up the chain of command; in dozens of interviews, he talked to army generals in Jakarta and to retired CIA agents living outside Washington. Anwar Congo, one of the most feared perpetrators - now a spritely, Hollywood-loving grandfather - became the main protagonist. At first he was boastful like all the other killers, but there was something different about him, Oppenheimer recalls. "I lingered on him because he was somehow honest and his pain was right at the surface."
In a chilling scene at the beginning of the film, Anwar does the cha-cha on a rooftop terrace where he dispatched many of his victims. He explains that he began by beating them to death but, because of the blood and the smell, switched to using a wire garrotte instead. Even as Anwar dances, "his trauma is already present", suggests Oppenheimer. "He had been trying to forget by drinking and doing drugs, and therefore became a playboy by dancing and going to nightclubs."
Anwar introduced Oppenheimer to the newspaper boss who would order whom to kill, and to Adi Zulkadry, another member of his death squad. (First seen in the film stepping off a plane wearing a T-shirt with the word "Apathetic" written across the chest, Adi claims he has never been troubled by sleeplessness, guilt or depression.) We also meet Herman Koto, a ponytailed hulk who comically tries to enter politics because of the opportunities for extortion, and leaders of Pancasila Youth, a paramilitary organisation heavily involved in the purge.
In a unique move, Oppenheimer invites the men to create fictional scenes, in the cinematic genres of their choice, to describe what they did. He films them putting the pieces together, and the increasingly disturbing and disorienting results. "Killing always involves some kind of distancing from what you are doing," he says. "Maybe that always means a kind of performance and acting, some kind of storytelling. Maybe it can just mean drinking first. But for Anwar, in part, it comes from the stories that he would imbibe in the cinema, the images and roles, the process of cinematic identification. The act of killing, for Anwar, was always some kind of act."
Anwar thought he could still distance himself from his trauma in this way. Instead, Oppenheimer says, "he found that acting for our re-enactments, he was reliving a kind of acting that he was going through at the time." Rather than abandon the process, Anwar embraced it; and midway through the shooting of the documentary, when the director suggested they go deeper into his nightmares, he "decided to explore through the filmmaking his own brokenness, his own trauma, his own pain". When Anwar casts himself as the victim in a noirish gangster movie scene and puts the wire noose around his own neck, he begins to understand what he has done. "That's not a conceptual idea that came from me," says Oppenheimer. "It's kind of an inevitable part of an emotional journey."
A horrifying re-creation of an attack on a communist village so blurs the line between reality and fiction that it feels like the filmmaker is losing his grip on the documentary. In fact, the raid and its upsetting aftermath look far worse than when they were filming, he says. Even so, there is a definite shift as "the fiction scenes take on a poetic truth, an emotional truth, that starts to take over the form of the film", he says, "so that it moves very much from being an observational documentary to being a kind of fever dream".
Oppenheimer admits there were times when he worried about collateral damage. When the ponytailed gangster Herman suggested Oppenheimer film how he makes a living, the director found himself following him and a Pancasila member as they extorted money from terrified Chinese shopkeepers. "I felt terrible because I knew that suddenly these Chinese shopkeepers, who are afraid of these men, now are confronted with the fact that, lo and behold, they're so powerful that they have their own foreign TV crew. So I would linger back, ostensibly to get a release form signed, but actually what I would do is try and explain what we were doing because I didn't want to add to their fear."
On another occasion, he realised when he was logging footage that he had filmed Anwar's neighbour tell a story about how his stepfather was murdered, and then go on, harrowingly, to play a torture victim as Anwar and Adi look on. (The neighbour has since died of diabetes.)
"When I put the film together I felt utterly exposed, I felt dirty, I felt tainted, I felt compromised," Oppenheimer admits. "But I felt at the same time that if it's my mistake that I allowed that to happen without my noticing, the fact that it happened - that he told this story and then they continued to work with him, having him play the victim - was more important."
It was an illustration of the men's sense of impunity that everyone needed to see. Because of Indonesia's censorship laws, however, The Act of Killing has not yet gone on general release there. Nevertheless, it has been seen, in a longer cut than the one shown in Berlin, at nearly 300 special screenings.
Disturbed by the film, the editor of the country's largest news magazine, Tempo, wondered if it was a repeatable experiment or whether the killers' openness was a response to something unique to Oppenheimer's methods.
"So they sent journalists all over the country to try and find killers who would talk about what they did in 1965. To their horror, they found that all over Indonesia the army had outsourced the killings to gangsters and criminals and rewarded them with power afterwards, and that these men were very happy to boast about the most grotesque, unthinkable things that they had done to other human beings."
They told stories similar to the one Anwar had recounted on the rooftop, they talked about burial pits, about slaughtering people in rivers, about killing people by firing squads, and about starving people in concentration camps. Tempo featured the testimonies and an extensive report on The Act of Killing in a double issue published in October.
"It broke a silence in the Indonesian media that has been in place ever since the killings," Oppenheimer says, "where no mainstream news or media outlet would even acknowledge that the killings took place."
It is now too risky for him to return to Indonesia. In an email exchange after the Berlinale, he tells me that he is still in contact with Anwar, with whom he's grown close, and that the killer watched the film for the first time in Jakarta in November. Afterwards, they'd talked by Skype.
"He started to cry," says Oppenheimer. "Tearfully, he told me: 'This is the film I expected. It's an honest film, a true film.' He said he was profoundly moved and will always remain loyal to it. I asked him how he felt during the screening, and he said, 'There is nothing left for me to do in life but die.' I tried to comfort him as best I could. 'You're only 70 years old, Anwar. You might live another 25 years. Whatever good you do in those years is not undermined by the awful things in your past.' It's a cliche, but it felt honest and it was all I could manage."
Now that The Act of Killing has opened a debate in Indonesia, Oppenheimer hopes it may lead to a nationwide investigation into the events of 1965. There are probably too many men (possibly as many as 10,000) like Anwar to put on trial ("I think you'd have a civil war if you tried") but the people really responsible - the army generals, majors, colonels and top paramilitary leaders - could be forced to testify in a commission.
Ultimately, he wants understanding. The Act of Killing doesn't seek to reassure us by painting the world in black-and-white moral certainties like much of the cinema beloved of Anwar. Rather, it forces us to see that the killers aren't so different from ourselves, which, perhaps, is the most troubling (and salutary) lesson of all.
"I think this film wants us to say: 'There's no good guys, there's no bad guys, there's just people.' That's its deepest message."