Deadpool co-creator is already on the outs with Marvel and has now slammed "impossibly dull and boring" Fantastic Four

Deadpool co-creator Rob Liefeld has given Fantastic Four: First Steps one of its harshest reviews to date.

"This was the 5pm Fantastic Four screening at my IMAX," Liefeld wrote on Twitter, accompanied by an image of a sparse-looking theater. "I can tell you why there is very little repeat biz on this film. It’s impossibly dull & boring."

Concerns over a weekday afternoon screening aside (typically one of the quieter periods across an opening week), Fantastic Four has performed admirably at the box office. First Steps earned just shy of $120 million domestically, with another $100m in its worldwide gross for a total of $218 million.

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It's worth noting that Liefeld has cut ties with Marvel over a perceived snub regarding a lack of invite to the afterparty for Deadpool and Wolverine's premiere, plus what he says was a lack of respect from Marvel Studios president Kevin Feige.

"It was meant to embarrass, diminish, defeat," Liefeld said on the Robservations podcast last year. "Disney is the deciding factor here. To have them say, ‘You and your family are not welcome here. We tolerated you for the screening.’ At that point, I knew in my heart I couldn’t go forward."

Audiences and critics may not agree with the Deadpool co-creator, however. It's currently soaring above Superman with its critical score on reviews aggregator Rotten Tomatoes, while it's at 92% on the fan-led Popcornmeter.

Next up in the MCU is Spider-Man: Brand New Day, which is currently filming. Know what that means? Leaks and announcements. That includes a major hint of Mister Negative, as well as the first official look at Tom Holland's new Spider-Man suit.

For more, check out our guide to upcoming Marvel movies. Then head on over to our spoiler-filled breakdown of the Fantastic Four: First Steps ending.