Joaquin Phoenix lost more than 50 pounds in preparation to play Arthur Fleck, aka Joker.

“The first thing for us was the weight loss. I think that’s really what I started with. And, as it turns out, that then affects your psychology. You start to go mad when you lose that amount of weight in that amount of time,” the actor said.

But that commitment to the role apparently has paid off — the critics love the movie, which opens Oct. 4.

“Nobody who sees this new film will ever need any other version,” writes David Sexton of the London Evening Standard.

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“Not to discredit the imaginative vision of the writer-director, his co-scripter and invaluable tech and design teams, but Phoenix is the prime force that makes Joker such a distinctively edgy entry in the Hollywood comics industrial complex,” writes David Rooney of The Hollywood Reporter.

Rotten Tomatoes, the movie review website, wrote a piece headlined: “JOKER FIRST REVIEWS: GIVE JOAQUIN PHOENIX THE OSCAR, ALREADY” (but so far, the film gets only an 83% rating, with some critics disliking the flick).

Over the last couple days, reviewers have seen screeners of the movie and most sing its praises.

“What a gloriously daring and explosive film,” Xan Brooks of The Guardian wrote.

“I am pleased to report that this movie is really, really good,” said Dan Casey of Nerdist.

“It’s going to turn the world upside down and make us all hysterical in the process. For better or worse, it’s exactly the movie the Joker would want,” said David Ehrlich of IndieWire.

“Joaquin Phoenix kills it in dark, timely DC origin movie that is no laughing matter. Will he be second Joker to win an Oscar?” wrote Pete Hammond of Deadline Hollywood.

“How does this Joker compare to previous portrayals?” Rotten Tomatoes wrote.

Joaquin Phoenix is throwing his hat in the ring for the title of “The Greatest Joker of All Time,” and he is a serious contender.

– Dan Casey, Nerdist [Phoenix has] crafted a layered, terror-inducing antagonist, and earned his rightful place alongside Heath Ledger and Jack Nicholson in the pantheon of all-time-great Jokers.

– Marlow Stern, The Daily Beast Nobody who sees this new film will ever need any other version.

– David Sexton, London Evening Standard

Another section of the RT piece asked “How disturbing is the movie?”

Joker offers up terrifying levels of tension. In fact, it’s scarier than most horror films of the year with its gritty, scary levels of realism.

– Brandon Davis, ComicBook.com There are moments of intense violence, but the dread is really the thing that will make you squirm, rather than gore.

– Jenna Busch, VitalThrills.com The mounting violence is intensely unpleasant, shocking if not particularly surprising; in scene after scene, the buildup is so agonizingly drawn out that you’re unsure whether the movie is depicting or embracing its protagonist’s cruelty.

– Justin Chang, Los Angeles Times The violence in this movie means to shock, and it does.

– Glenn Kenny, RogerEbert.com

Joker is dark only in a stupidly adolescent way.

– Stephanie Zacharek, Time

Below are the two trailers released so far.