Horror movies make death easy. Lots of people find them hard to watch, of course, but they ultimately make the loss of life a consumable commodity – with the swipe of a machete, the slash of a knife, the plunge of a handful of razors, humans expire. A series of these makes for a fast-moving popcorn picture.

Even the most gratuitous cases are relatively breezy. The pièce de résistance of the bled-dry torture porn genre, the Saw franchise, featured a series of hideously inventive, Rube Goldberg-esque deaths that, per the guiding hand of serial killer Jigsaw, generally took just a minute to carry out (with, say, another minute or so of setup). A great way to take the edge off extremeness is to make it mercifully brief. Mass murders are common in entertainment but not so much in the typical American life – those of us privileged to a peaceful existence can write off an eyeful of carnage with, "It's only a movie."

Michael Haneke's Palme d'Or-winning Amour is not a conventional horror movie, but it is among the most brutal pieces of cinema I have ever experienced. No heads roll, no blood flies, there isn't even a sense of suspense in this French-language film – just an elderly woman who decays before our eyes, while hers slowly drain of life via a performance from Emmanuelle Riva that is among the very best this or any year has offered. This genius woman is a vessel for Haneke's unflinching affliction of suffering on his audience.

There's not even a single cause given to explain the decline of Riva's Anne. One day, she sits with her affectionate husband ("Did I mention you looked pretty tonight?" he asks her early on), Georges (Jean-Louis Trintignant) and zones out. It takes her a disconcerting amount of time to snap out of it. This is the moment that their shared life has led up to, the tragedy that every day brought closer. There's one waiting for all of us. And then more.

A botched operation follows, leaving her paralyzed. Then a second stroke. It all rolls out so slowly in a series of long scenes of vain attempts at rehabilitation that seem to amount to a big bunch of domestic nothing until they serve as harrowing contrast to Anne's living decay. Eventually, she struggles to sing. She can barely choke down three bites of applesauce. She ends up with more water on her chest than in her mouth when Georges attempts to make her drink. She winces at a sponge bath, moaning, "Hurts." She lies in bed doing the same, over and over and over.

I was reminded of Haneke's smugly self-aware Funny Games during an exchange in which Georges justifies ignoring the calls of his daughter Eva (Isabelle Hupper) – it's all too bleak, this series of highs and lows, Anne's recalling her childhood, being able to choke down a few bites of food, bursting into maniacal laughter. Some of this we have seen, some we have not. "Not all of that deserves to be shown," explains Georges. For as hard to watch as all of this is, it gets worse.

"It will go steadily downhill and then it will be over," Georges explains with the evenness of a sociopath. Clearly, no happy ending is in store, but the one Haneke devises is more complex than what seems to be set up, one that questions the nature of mercy and whom what we refer to as "love" serves most – the loving or the beloved. Early on, when she is still mostly present, Anne tells Georges, "I don't want to go on," after he attempts to convince her that taking care of her in her fragile state will be his duty and his pleasure. He becomes a conduit of her suffering, a symbol of love's cruelty.

Amour is a movie of rot, one in which kindness and empathy devolve into euphemisms for selfishness. More horrifyingly, it exploits our fears of old age and notions of inevitability – in the best-case scenario, we grow old with the person we love the most while facing misery. Though the performances are vivid enough ("died-in" seems better than "lived-in" to describe Riva's astounding turn) to provoke sadness, the primary emotion I felt was dread. This movie is punishing and an utterly brilliant entry in the cinema of death. I hope to never see it again. I hope I can never relate to it, but I know that I will – if I'm lucky.