After a long hiatus, Natalie Portman is set to return to Thor as Jane Foster in Thor: Love And Thunder, which is coming to theaters on July 8. And while fans are counting down the minutes to see Chris Hemsworth again, not everyone is as excited about the return of Jane Foster. Reason? Fans cite the lack of chemistry between Portman and Hemsworth.

Chemistry is very important on screen and it can make or break a movie. It is often the most prevalent reason why a couple does not convince the audience. It's why most casting directors do the so-called "chemistry tests" between co-stars before the final casting. Despite that, there are still occasions where a couple just doesn't work, and users of Reddit didn't hesitate to point it out.

Padme And Anakin (Attack Of The Clones)

Padme and Anakin Skywalker in Attack of the Clones

"The most obvious one is Attack of the Clones. I can’t think of any pairing more boring and lifeless than Hayden Christensen and Natalie Portman. c3PO and R2-D2 have more romantic chemistry than they do," the Reddit user Safe_Ad4352 said in the thread.

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Despite Star Wars being one of the most beloved franchises of all time, fans didn't seem to buy what these two were selling at the time. This might have had something to do with the fact that it was one of her first big-budget movies, and at the time of filming the first, she was only 16 years old. Perhaps it was just a poor casting choice.

Reed Richards And Susan Storm In The Fantastic Four

Jessica Alba and Ioan Gruffudd in Fantastic Four with a judging expression.

"Mr. Fantastic and the Invisible Woman in the Fantastic Four movies. Jessica Alba had no chemistry with Ioan Gruffudd and the most sexual tension in the films was between Alba and Chris Evans. Creepy" said Reddit user dialcforcasey.

It's quite incredible how two fantastic-looking people can have zero chemistry at all. And sadly that was the case in Fantastic Four. It's clear something has gone wrong when people start noticing an actress has more chemistry with her on-screen brother than her love interest. With Fantastic Four joining MCU and Disney in search of a director, they hopefully won't make the same mistake.

Harry Potter And Ginny Weasley (Harry Potter)

Harry and Ginny stare at George in Harry Potter

It's obvious that because not all Harry Potter books were published at the time of the first movie, the producers didn't know that Harry and Ginny would end up together when casting Wright as Ginny. According to some people, their romance doesn't even make sense. It's also quite impossible to check for chemistry with kids, and Bonnie Wright was only nine when she appeared in the first Harry Potter film.

But nobody could have expected just how awkward and horrible the portrayal of that relationship was. The actors weren't the only ones to blame though. The Reddit user moonkittys pointed out: "Harry and Ginny in Harry Potter. Their romantic scenes were incredibly awkward and they had 0 chemistry. The kiss scene in the room of requirement and her tying his shoes scene... bleh, they're all bad."

Superman And Lois Lane (Man Of Steel/DC Universe)

Superman Carries Lois in Batman V. Superman

While fans seemed to like the respective actors in these roles, especially Cavill as Superman, the relationship did not convince everyone. Reddit user zacweso shared: "I feel like the films also didn't do them any favors in relationship building either. I was trying to finish the Snyder cut this weekend and the initial reunion between Lois and Clark feels like people who haven't even met before."

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This is particularly obvious when the love story in question is one of the most famous and epic in the source material . It's clear that the superhero franchises don't like to focus on romance too much, but Lois has always been a part of Superman's journey. Perhaps this was not so much a question of chemistry, but their relationship simply required a better build-up.

Aquaman And Mera (Aquaman)

Amber Heard and Jason Momoa in Aquaman

According to Rolling Stone, the Warner Bros executives were at one point considering recasting Amber Heard because of her lack of chemistry with Jason Momoa. Executives were not the only ones who noticed, as Reddit user smokeehayes mentions them on their less-than-flattering list.

Though the recasting never happened, the executives did admit that it took a lot of work and post-production magic to achieve the final result. Not even that can fool the most loyal fans, who saw right through the attempts. Sometimes editing can do the trick, but if the chemistry is truly not there, no amount of movie magic will help.

Anastasia Steele and Christian Grey (50 Shades Trilogy)

Fifty Shades Darker Poster Ana Steele Christian Grey

Reddit user latche says: "Any answer I give will very soon be eclipsed by Anastasia Steele and Christian Grey. Like watching two blueberries together." This movie franchise has been under a lot of scrutiny, even though it never pretended to be something it's not.

However, these two do appear in more than one thread on the subject, which is surprising, because surely a movie adaptation of an erotic novel did a chemistry test between their leads. The Fifty Shades trilogy isn't everyone's cup of tea, and it doesn't pretend to be the greatest love story of all time, but it is about sex. Therefore chemistry is a must.

Harry And Sally (When Harry Met Sally)

Meg Ryan and Billy Crystal in When Harry Met Sally standing together in a park probably NYC

Reddit user Typical_Humanoid agrees with the original vote: "WHMS is what I was going to mention. I actually am a bit of an incurable romantic but this is one movie where remaining platonic would've been exactly what the movie needed."

As one of the most beloved romantic comedies of all time, this stance is surprising, but it's not rare. Many people in the threads agree that this should have stayed a platonic relationship and that it would have been better for the movie in the end. It's quite often that actors can play friends but lack romantic chemistry. Harry and Sally still take first place in the friends-turned-couple category though, so clearly, at least some people disagree with Reddit.

Marissa And Christopher (Maid In Manhattan)

A still from Maid In Manhattan of the protagonists dancing.

Reddit user NoHandBananaNo said: "Jennifer Lopez and Ralph Fiennes in Maid In Manhattan. Zero chemistry and zero believability." When someone thinks of Ralph Fiennes, they don't think of romantic comedies, and surely it has taken more than one HP fan to connect the dots and realize that their favorite childhood villain is the love interest in this flick.

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This is likely due to the fact that he just excels in other types of movies, and it's what he sticks to most of the time. But actors aren't fully to blame. Despite the intention being a romantic story where the underdog prevails, it was highly unbelievable in the first place that someone as rich as him would even look at a maid twice.

Peter Parker and MJ (Spiderman 2002)

Kirsten Dunst and Tobey Maguire lying in a web in Spider-Man 3

Reddit User AndrewCole14 "Despite dating in real life Tobey Maguire and Kirsten Dunst had absolutely no chemistry in the Spider-Man movies." And it's impossible to disagree with that statement. The casting for this couple was unfortunate, and as other Reddit users pointed out, Peter had more chemistry with Ursula than he did with MJ.

Their possible real-life romantic history aside, the couple at least does have one iconic if bizarre moment that viewers will never forget with the upside-down kiss that nearly drowned Tobey Maguire.

Jane Foster And Thor (Thor)

Jane Foster talking to Thor on Asgard.

Jane Foster is one of the characters returning to MCU in the next Thor movie, and fans had a lot to say about the chemistry Natalie Portman shared with Chris Hemsworth. This Redditor had to share his girlfriend's opinion: "My girlfriend wants to add that the love story between Thor and Natalie Portman's character is so forgettable and devoid of chemistry that it practically ruined the story."

But people were quick to defend these two, saying it had more to do with the dialogue than anything else. The character of Thor has grown and has been through a lot, especially in Endgame, so it will be interesting to see if they work better together in the upcoming one.

NEXT: The 10 Best Movie Couples, According To Reddit