The aim of the Joker has always been to sow chaos and panic in the citizens of Gotham City. In this, Todd Phillips’ origin story seems to have succeeded, given the amount of lip service paid to worries that “Joker” will weaponize volatile viewers.

Its final act is, indeed, bracingly over the top, as Joaquin Phoenix’s Arthur Fleck sheds his sad-sack chrysalis and emerges into full-blown Joker mode. It’s horrifying, it’s artful — and it’s hardly alone in its cinematic zest for violence. (Just ask John Rambo, back at the box office a couple weeks ago.)

The rest of “Joker” is, in essence, a compelling character study — one whose appeal may be limited to Batman completists, of whom there are certainly quite a few. Let’s be clear, this is no comic-book romp. It’s a seriously dark urban drama about a charmless schlub (Phoenix) saddled with a brain injury that gives him an inadvertent cackle, caring for his ailing mom (Frances Conroy) and working a lousy gig as a rent-a-clown while nursing dreams of being a stand-up comic. This oddball, vulnerable soul gets beaten up — literally by goons, figuratively by the healthcare system — and then beaten up again. Eventually, he can’t take it any more. You see where this is going. And where its roots lie.

If the casting of Robert De Niro as a late-night talk show host wasn’t enough to tip you off, the mood and look of “Joker” is deeply rooted in (not to say derivative of) the gritty New York dramas of the ’70s and ’80s, particularly “Taxi Driver,” “Death Wish” and “The King of Comedy” — the latter of which starred De Niro as a creepy stalker obsessed with a popular entertainer.

It’s a different take on the DC comics character, and why not? The Joker’s an anarchic villain for the ages, still wide open for interpretation even after countless portrayals. We all have our favorites — Heath Ledger’s mine, though I’ll never forget my first, Cesar Romero — but there’s no reason someone else can’t take a crack at it.

Who better than crazy-eyed Joaquin Phoenix? The actor’s physicality here is something to behold. It’s never quite clear why Arthur’s so emaciated, but the way he contorts his spindly frame, and occasionally stretches it out into a joyful, Kabuki-esque dance, is mesmerizing.

Phoenix’s tic of a laugh is, indeed, disturbing, though it always seems vaguely forced. I’m hardly the biggest DC fangirl, but it strikes me that the whole point of the Joker is that he gets bubbly joy out of the most horrible things in the world. To relegate his giggling to a neurological injury sort of defangs the concept.

“Joker” starts grim and gets grimmer, as Arthur embraces his inner demons and finds they resonate with the huddled masses of Gotham. When he dispatches some Wall Streeters who taunt him on the subway — in shades of reverse Bernhard Goetz — he spawns a clown-faced “Kill the rich” movement that hints at his future potential as a charismatic supervillain.

No doubt some will balk at their favorite comics character being dragged down into such gloom and doom. The director had, I think, a solid defense in referencing the 1988 graphic novel “Batman: The Killing Joke,” at my screening, in which the Joker says, “I prefer my past to be multiple choice.” He’s a slippery chameleon with a host of backstories. If this one seems depressingly reflective of our own reality, well, it’s brought to you by the guy who’s been yukking it up about male bad behavior for years in movies like “Old School” and “The Hangover.” I like to imagine that Phillips embedded this one with a wry message: Toxic masculinity is, actually, no joke at all.