Since 2008’s “Iron Man,” the Marvel machine has been one of the most unstoppable forces in box-office history. Now, though, that aura of invincibility is showing signs of wear and tear. The superhero factory hit a new low with the weekend launch of “The Marvels,” which opened with just $47 million, according to studio estimates Sunday.

The 33rd installment in the Marvel Cinematic Universe, a sequel to the 2019 Brie Larson-led “Captain Marvel,” managed less than a third of the $153.4 million its predecessor launched with before ultimately taking in $1.13 billion worldwide.

Sequels, especially Marvel sequels, aren’t supposed to fall off a cliff. David A. Gross, who runs the movie consulting firm Franchise Research Entertainment, called it “an unprecedented Marvel box-office collapse.”

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The previous low for a Walt Disney Co.-owned Marvel movie was “Ant-Man,” which bowed with $57.2 million in 2015. Otherwise, you have to go outside the Disney MCU to find such a slow start for a Marvel movie − releases like Sony’s “Morbius” in 2022 or 20th Century Fox’s “Fantastic Four” reboot with $25.6 million in 2015.

But “The Marvels” was a $200 million-plus sequel to a $1 billion blockbuster. It was also an exceptional Marvel release in numerous other ways. The film, directed by Nia DaCosta, was the first MCU release directed by a Black woman. It was also the rare Marvel movie led by three women: Larson, Teyonah Parris and Iman Vellani.

Reviews weren’t strong (63% fresh on Rotten Tomatoes) and neither was audience reaction. “The Marvels” is only the third MCU release to receive a “B” grade on CinemaScore from moviegoers, following “Eternals” and “Ant-Man and the Wasp: Quantumania.”

“The Marvels,” which added $63.3 million in overseas ticket sales, may go down as a turning point in the MCU. Over the years, the franchise has collected $33 billion globally, a point Disney noted in reporting its grosses Sunday.

But with movie screens and streaming platforms increasingly crowded with superhero films and series, some analysts have detected a new fatigue setting in for audiences. Disney chief executive Bob Iger himself spoke about possible oversaturation for Marvel.

“Over the last three and a half years, the growth of the genre has stopped,” Gross wrote in a newsletter Sunday.

Either way, something is shifting for superheroes. The box-office title this year appears assured to go to “Barbie,” the year’s biggest smash with more than $1.4 billion worldwide for Warner Bros.

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Marvels has still produced recent hits. “Guardians of the Galaxy Vol. 3” launched this summer with $118 million before ultimately raking in $845.6 million worldwide. Sony’s “Spider-Man: Across the Spider-Verse” earned $690.5 million globally and, after rave reviews, is widely expected to be an Oscar contender.

The actors’ strike also didn’t do “The Marvels” any favors. The cast of the film wasn’t permitted to promote the film until the strike was called off late Wednesday evening when SAG-AFTRA and the studios reached an agreement. Larson and company quickly jumped onto social media and made surprise appearances in theaters. And Larson guested on “The Tonight Show” on Friday.

The normally orderly pattern of MCU releases has also been disrupted by the strikes. The only Marvel movie on the studio’s 2024 calendar is “Deadpool 3,” opening July 26.