"If a B character from Marvel shut downs?and outperforms the A team from DC, that’s an embarrassment," a Justice League insider tells The Hollywood Reporter, adding, "It’s going to be a stressful weekend for some [Warners]?execs."

For Warner Bros., Justice League is tracking for a $110 million debut, dramatically behind the massive $166 million Batman v. Superman grossed in March 2016. And inside Warners, expectations are muted for Justice League, which has received very mixed reviews from top critics. The film's tumultuous shoot included Zack Snyder exiting following a family tragedy and Joss Whedon stepping in to oversee extensive reshoots that cost millions. Sources say the studio has higher hopes for the solo movie Aquaman, which hits theaters Dec. 21, 2018.

Meanwhile, on Nov.?7, days after Ragnarok opened to $122.7 million in the U.S., DC Comics lured superstar Brian?Michael Bendis away from Marvel, where he had spent the past 17 years penning best-sellers including Ultimate Spider-Man and The Avengers, which helped inspire multiple films and TV shows. Bendis inked a “multifaceted” deal that sources say could give him input on Warner Bros.’ growing?stable of DC films.

While Marvel put on a professional face, calling Bendis a great partner and complimenting his creativity and professionalism, several?sources tell THR that staffers were surprised by the poaching move. “He was one of the people I thought would never leave,” says author Reed Tucker, whose book Slugfest chronicles the heated rivalry between the two comic companies. “I was shocked.”

Friendly rivalry has been in the companies' DNA since the 1960s, when Marvel's Stan Lee would insert jabs at DC into his comics, characterizing the competitor as square and Marvel as the hip underdogs. DC would respond by ribbing Lee as a grandstanding self-promoter.

Things went from friendly to ugly in the 2000s, culminating with a now-legendary 2002 interview in which then-Marvel editor-in-chief Joe Quesada mocked DC for not having more success on the big-screen, despite owning characters as popular as Batman and Superman: "That’s like being a porn star with the biggest dick and you can’t get it up."

It's a wound that never quite healed. And the rise of social media has helped create a news ecosystem as polarized as the cable news networks, one in which DC and Marvel fans only seek out positive news about their respective companies.

Even James Gunn, director of Marvel's Guardians of the Galaxy, recently took to Twitter to urge fans to make peace with one another, writing, "So why do you spend so much time raging at each other? It’s silly. Please just stop it. Stop engaging in that way."

“I’ve never seen fans get so worked up. It’s a weird subculture of fans that is making things worse," says FJ DeSanto, a writer-producer of Transformers: Prime Trilogy and self-proclaimed fanboy.

Chris Begley, founder of the Batman-focused fan site Batman-News, notes that traffic surges around controversial issues, such as rumors of Ben Affleck leaving his role as Batman, with readers swarming to condemn his site for even posting news that would suggest such a thing. "Some hardcore DC fans only want to read 'good news,'" he says.

Perhaps because Marvel has been riding high with its films, its die-hard fans are less likely to take criticism of the company personally, notes Lauren Gallaway, who runs the fan site The Marvel Report. When Marvel and Netflix's Iron Fist was accused of cultural appropriation, it led to productive conversations about representation online. "With Marvel, typically the only thing that triggers people is race," says Gallaway.

While on the big screen Marvel has remained dominant, both companies have had mixed returns on the small screen. DC is on surer footing with its slate on The CW, where it underpins the broadcaster. Marvel has found some acclaim with its Netflix shows that offset broadcast network critical disappointments like Agents of SHIELD and The Inhumans.

For DC, the stakes with Justice League could go beyond box-office dollars and bragging rights. "For a lot of people who are following DC Cinematic Universe, Justice League is the last chance for them to get it right," says Tucker. "If it's as reviled as Batman v Superman, I think some of the fans are going to check out."

Lesley Goldberg contributed to this story.

A version of this story first appeared in the Nov. 15 issue of The Hollywood Reporter magazine. To receive the magazine, click here to subscribe.