Watch: Final full trailer for Joaquin Phoenix's gritty Joker film lands

Joaquin Phoenix plays Arthur Fleck, an aspiring comedian struggling with life in 1970's Gotham. Photo / AP.

The final full trailer for Joker was released today, giving fans a deeper look at Joaquin Phoenix's dark portrayal of the maniacal DC villain.

Directed by Todd Phillips (The Hangover), Joker will premiere at the Venice Film Festival this week before landing in cinemas on October 4.

The new trailer shows more of Phoenix as aspiring comedian Arthur Fleck struggling with life in 1970's Gotham, and his transition into the psychotic Clown Prince of Crime, known as Batman's arch nemesis.

The new film, inspired by Taxi Driver, has an R rating due to its graphic violence, sex, disturbing behaviour, and strong language. It looks much darker than Christopher Nolan's hugely popular Dark Knight Batman franchise and other previous child-friendly portrayals.

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Final trailer. #JokerMovie - in theaters October 4. Link in Bio!

A post shared by Todd Phillips (@toddphillips1) on Aug 28, 2019 at 9:01am PDT

"We didn't follow anything from the comic books, which people are gonna be mad about," Phillips told Empire magazine.

"We just wrote our own version of where a guy like Joker might come from. That's what was interesting to me. We're not even doing Joker, but the story of becoming Joker. It's about this man."

The trailer shows the down on his luck Fleck growing increasingly disillusioned and frustrated by the world around him.

When a counsellor breaks the news to him that they will no longer be meeting, he replies: "You don't listen do you? You just ask the same questions every week. How's your job? Are you having any negative thoughts?

"All I have, are negative thoughts."

Joaquin Phoenix in a scene from the upcoming Joker movie directed by Todd Phillips. Photo / AP.

Phoenix, who has previously steered clear of comic book films, was initially reluctant to take on the role, but the subtlety and depth of the character convinced him it was the right move.

"It took me a while [to commit]," he told Total Film. "Now, when I look back, I don't understand why.

"I think oftentimes, in these movies, we have these simplified, reductive archetypes, and that allows for the audience to be distant from the character, just like we would do in real life, where it's easy to label somebody as evil, and therefore say: 'Well, I'm not that'."

The film also stars Robert De Niro as a TV talk show host named Murray Franklin, along with Zazie Beetz, Frances Conroy, Marc Maron and Brian Tyree Henry.