Marvel is currently the undisputed king of the comic book superhero movie genre. The Marvel Cinematic Universe is an all-conquering behemoth; a collection of massive franchises that somehow still tells a cohesive story across multiple films and many different corners of the Marvel world. In 2018 alone, between Avengers: Infinity War, Black Panther and Ant-Man and the Wasp MCU films made over $4 billion at the worldwide box office. Fox and Sony are also cashing in big on the Marvel name with their X-Men, Deadpool and Venom films. However, it really wasn't so long ago that Marvel characters had a truly embarrassing record on the big screen. Before 1998's Blade and 2000's X-Men made audiences take comic book movies seriously again, Marvel had a terrible cinematic run that included Howard The Duck (1986), direct-to-home-video disasters like The Punisher (1989) and Captain America (1990). There was even a 1994 Fantastic Four movie made by Roger Corman that was never released officially to the public, instead existing primarily as a bootleg video at conventions!

During this fallow period (and even as Marvel began to experience success), there were a huge number of characters fans thought they'd never see on the screen, for a variety of reasons. Maybe they thought the character concept was too outlandish for mainstream audiences to accept? Or that the character design would require expensive CGI or unwieldy make-up effects that an actor was unlikely to agree to? Maybe the character's backstory required too intimate a knowledge of obscure Marvel lore and would therefore be difficult to streamline for the screen? In any case, here are 20 Marvel characters we thought would be impossible to bring to the screen.

20 GALACTUS

Galactus Fantastic Four Rise of the Slver Surfer

In terms of character's deemed impossible to bring to the screen, there are few more troublesome than Galactus, the Devourer of Worlds. Comic book fans have gotten used to the idea of a cosmic entity towering in the sky while wearing a somewhat bizarre blue and purple costume and pointy helmet. But when Fantastic Four: Rise Of The Silver Surfer was being made in the mid-2000s, Fox wanted the character design to look 'discreet'.

We imagine that to be studio spin for :we don't want general audiences to think that a big purple guy in the sky eating planets looks silly". They instead opted to show Galactus as a cosmic cloud, which didn't go over well with fans at all. Impossible? Maybe not. But certainly very difficult to realize on-screen.

19 THANOS

For the longest time fans thought they would never see the "Mad Titan" Thanos on the big or small screen. A mutant member of a race of superhumans known as the Titanian Eternals, Thanos has more superpowers than you can shake a stick at and is considerably larger and more imposing than even the biggest human.

Fortunately, by the time the Marvel Cinematic Universe sought to include him in their rich tapestry of films, computer generated imagery and pioneering motion capture technology had reached a point where Thanos was finally possible. Actor Josh Brolin's excellent, soulful and intimidating performance in Avengers: Infinity War shone through all the special effects and the character became an instantly iconic villain.

18 GROOT AND ROCKET

Guardians of the Galaxy Vol. 2 Groot Rocket Raccoon

Before the 2014 movie made the Guardians Of The Galaxy unlikely superstars, the team was a semi-obsure element of the Marvel Universe. In fact, the lineup in the movie consisting of Star-Lord, Gamora, Drax etc had only been operating in the comics since 2008, when the Guardians concept was resurrected after 13 years in stasis.

Fans were therefore understandably nervous about the movie being the MCU's first flop, but it wound up being one of the best Marvel movies ever thanks in no small part to the hilarious and unexpectedly poignant takes on Rocket Racoon and Groot. Bradley Cooper's sarcastic vocal performance as Rocket was amazing and they somehow managed to make people care deeply about a humanoid tree only capable of saying three words!

17 GHOST RIDER

Ghost-Rider-2007

Ghost Rider has been featured on the big screen twice, with decidedly awful results. The Johnny Blaze version of the character was played by Nicolas Cage in 2007's self-titled film and its 2012 sequel/unofficial reboot Ghost Rider: Spirit Of Vengeance. Both movies were critically mauled and they seemed to prove that the character, a demonically possessed stunt motorcyclist with a flaming skull for a head, wasn't meant for a live-action depiction.

It was too ghoulishly silly and the CGI left a lot to be desired. But, the Robbie Reyes version was then included in the Agents Of S.H.I.E.L.D. TV show in 2016, with better (if still not definitive) results. Maybe a truly brilliant screen version of the character is impossible, but we're sure Marvel will try again.

16 JUGGERNAUT

Vinne Jones' Juggernaut in his helmet in X-Men: The Last Stand.

Cain Marko, aka Juggernaut, has long been one of the X-Men's most popular and enduring villains. Professor Xavier's half-brother, he was transformed into a massive, hulking beast by the mystical Gem Of Cytorrak. Juggernaut's physical dimensions are so comically large that if he was ever to be translated to film, fans knew it would have to be a fully CGI job, like Hulk.

Naturally, X-Men: The Last Stand's filmmakers then put British soccer-player-turned-actor Vinnie Jones in a muscle suit that barely made him look bigger than Hugh Jackman's Wolverine -- it was embarrassing. The character then appeared again, thankfully in full CGI mode, in Deadpool 2. This was much better (although still played for laughs) and there was no mention of his comic book origin.

15 NIGHTCRAWLER

The X-Men movies did a much better job in bringing Kurt Wagner, aka Nightcrawler, to the screen. Played by Scottish actor Alan Cumming in X2: X-Men United, the German-born blue-skinned mutant was realized brilliantly. He wasn't a 'fuzzy elf', but Cumming was warm and likable, even beneath the state-of-the-art makeup effects covering his body.

He also successfully portrayed the dichotomy between Nightcrawler's demonic appearance and his profound Catholic belief system. A character that would have been easy to mess up, we're calling this one a big win. Kurt Wagner was then played again by Kodi Smit-McPhee in X-Men: Apocalypse, but didn't have enough screen-time for fans to really generate a full opinion on the new portrayal.

14 ANT-MAN AND THE WASP

Due to the project's long-term rest in development hell, fans believed for almost a decade that Ant-Man was never going to make it to the big screen. Beloved director Edgar Wright (Baby Driver) was hired in 2006 to develop a film, before the birth of the MCU. He delivered multiple script drafts and even shot test footage over the next eight years, but finally dropped out in 2014 due to creative differences with Marvel.

Miraculously, director Peyton Reed then stepped in and made two critically acclaimed Ant-Man movies, including Evangeline Lilly's The Wasp as a title character in the sequel. He embraced the concept's inherent potential for amusing silliness but also the potential for groundbreaking shrinking and growing CGI effects.

13 VENOM

Tom Hardy as Venom

Another character that was stuck in development hell for years, many Marvel fans lost hope of ever seeing a truly faithful representation of Venom on-screen. The Topher Grace incarnation that was shoe-horned into 2007's Spider-Man 3, much to the chagrin of director Sam Raimi (who has always been brutally honest about Sony forcing him to include the character in that movie) left a bad taste in most people's mouths.

But then, after 11 years and a huge amount of false starts, Venom finally hit the big screen again a few weeks ago in a solo movie which broke box office records, despite some extremely negative reviews. Fans generally seem to love Tom Hardy's performance, so this is a certainly a case of perseverance paying off in the end!

12 DOCTOR OCTOPUS

Spider-Man-2-Doctor-Octopus

Despite being arguably the second most iconic Spider-Man villain in history (only coming second to Norman Osborn/Green Goblin, of course), Otto Octavius, aka Doctor Octopus, has only appeared on the big screen once. He has a litany of animated incarnations, but in terms of live-action only Alfred Molina's version of the character from Sam Raimi's Spider-Man 2 exists.

Molina's performance was incredible and is still beloved to this day. Brilliantly, perhaps the most wonderful thing about the character was the very thing fans were most nervous about: his deadly mechanical arms. Running the risk of looking ridiculous, the arms instead looked awesome. Imbued with a snake-like personality and a vicious streak a mile wide, they were a joy to watch.

11 ULTRON

Ultron

The villainous robot Ultron, nemesis of the Avengers, has a very complicated backstory in the comics. He was originally introduced under the monicker "Crimson Cowl" and was created by Hank Pym, aka Ant-Man. Ultron would then in-turn create the Vision and be the first character in the Marvel Universe to use the unbreakable metal adamantium (which would of course later be bonded to Wolverine's skeleton).

Given that the MCU couldn't use adamantium, Hank Pym was depicted as an old man and Vision hadn't appeared yet, the makers of 2015's Avengers: Age Of Ultron had a tough (almost impossible) task bringing Ultron to the screen. In the end, Tony Stark using Loki's scepter to create a sarcastic psychobot wasn't exactly the most elegant solution.

10 ARNIM ZOLA

Arnim Zola Lamest MCU villains

Arnim Zola has to be one of the goofiest looking Marvel villains in history. Originally an evil scientist during World War II, he survived into the modern day by transferring his consciousness into the body of a robot, which projected his face on a screen on its chest plate. All in all, not really a character many fans imagined being translated 100% faithfully to the screen.

To their credit, Marvel took an approach that honoured the comic book origins while dialling down the silliness considerably. Toby Jones played Zola the human scientist in Captain America: The First Avenger and then reappeared in the modern-day sequel Captain America: The Winter Soldier, with his consciousness transferred into a '70s-era supercomputer. Nice job, Marvel.

9 RHINO

Rhino destroys the street in The Amazing Spider-Man 2

Paul Giamatti is one of the most talented and respected character actors in Hollywood, known for bringing an element of gravitas to any role. To say it was therefore bizarre to see him show up in the two bookending scenes of The Amazing Spider-Man 2 as Aleksei Sytsevich/Rhino, complete with comedy Russian accent, would be an understatement.

Chewing the scenery in a manner that would've made Jack Nicholson's Joker blush, his performance was truly forgettable. Sadly, the mechanical suit of armor that the filmmakers went with, instead of the traditional thick polymer suit that resembles a rhinoceros hide, was also underwhelming. Perhaps they should've left Rhino out of the movie entirely, as their depiction was bad in every way.

8 APOCALYPSE

Apocalypse in X-MEN: APOCALYPSE using his powers

When X-Men was released in 2000, the filmmakers took a deliberately grounded approach to Marvel's merry mutants. At this point, comic book m0vies were out of vogue, so they didn't want to highlight the more outlandish aspects of the source material. At this point, the idea of En Sabah Nur, aka Apocalypse, ever being brought to the screen would've seemed utterly impossible.

The world's first mutant, dating back to ancient Egypt, Apocalypse was a blue-skinned behemoth with access to almost every power imaginable. But, by the time 2014's X-Men: Apocalypse rolled around, the world was much more accustomed to superheroes and their heightened worlds. Unfortunately, the movie (and Apocalypse in particular) was a dud. Swing and a miss!

7 DORMAMMU

dormammu in MCU

The "Dread One" Dormammu has long been arch-nemesis of Doctor Strange, so it was only fitting that he would make an appearance in the character's debut movie. However, given that the film had to establish the character of Stephen Strange and the world he operated in, as well as The Ancient One and Mordo (his mentors in the mystic arts) and functional villain Kaecilius, it left little room for a fully-fleshed out depiction of the ancient interdimensional demon.

The solution of having Dormammu appear as a bodiless entity in the Dark Dimension was fairly elegant and left room for the character to potentially be explored further in future movies. This re-imagining yielded much greater success than when Galactus became a cloud, that's for sure!

6 X-23

X-Men X-23 Logan Daphne Keen

Generally speaking, watching children committing aggressive acts in movies is not something audiences or filmmakers want to deal with. It's usually reserved for horror movies or harrowing family dramas and much of the acts tend to take place off-screen. X-23, Wolverine's clone and a child forced to take lives by her creators, would therefore have been a very dicey proposition.

But, perhaps buoyed by the positive response to Chloe Moretz' Hit-Girl in 2010's Kick-Ass, X-23 did make her way to the screen in all her tragically ultra-violent glory in 2017's Logan. The movie refused to shy away from the unpleasantness of her (and Logan's actions) and Dafne Keen's performance was revelatory. A new comic book movie icon had been born.

5 DEADPOOL

Deadpool 2 Deadpool X-Force

Deadpool referred to himself as 'Ryan Reynolds crossed with a Shar-Pei' in a 2004 issue of Cable and Deadpool. Fans always wanted Reynolds to play the character, so we were distraught when he finally showed up in 2009's X-Men Origins: Wolverine in an offensively inaccurate representation of the character.

Everyone thought a faithful movie version of Deadpool was impossible, if this was how Fox would treat the character. But Reynolds refused to give up, and after years of persistence he and director Tim Miller finally convinced the studio to part with $58 million to make a true Deadpool movie. It was a gargantuan hit, led to an equally successful sequel and Deadpool is now a genuine A-list mainstream superhero icon. Go figure!

4 VISION

MCU's vision

We mentioned earlier that, in the original Avengers comics, the android Vision was created by Ultron as a weapon to use against his creator Hank Pym. The character went on to become a mainstay on the superhero team, as readers watched him try to become more "human" while forming a famous romantic relationship with Scarlet Witch.

A red-skinned android, with a personality similar to Spock from Star Trek, who romanced a human (well, mutant) woman while also serving on a superhero team would've been a tough proposition for most movie studios. So what did Marvel do? Very faithfully translated his story to the screen, with some tweaks. And you know what? It worked, due to Paul Bettany and Elizabeth Olsen's performances.

3 EGO THE LIVING PLANET

Ego MCU

It's amusing to imagine what actor Kurt Russell (The Thing) first thought when he was initially approached to play Ego the Living Planet in Guardians Of The Galaxy Vol 2. Created by comics maestros Jack Kirby and Stan Lee in 1966, Ego was a big purple planet with a face on it. He was the result of a human scientist merging with a planet when the sun went supernova.

A concept that could only work in comic books, right? According to writer/director James Gunn, wrong. He re-wrote Ego as Peter Quill's father, a Celestial being who used his powers to form an entire planet around him. He wanted to remake all worlds into extensions of himself and had ended Quill's mother after his love for her interfered with his plans. Against all the odds, it worked!

2 COLOSSUS

Stefan Kapicic Colossus

Colossus' appearances in the two recent Deadpool movies have been true highlights of the films. The excellent motion capture CGI technology captures his giant frame and shiny metallic skin perfectly and Serbian actor Stefan Kapicic's vocal performance is both endearing and hilarious.

However, it's easy to forget that Piotr Rasputin also appeared in three previous X-Men movies, played by Daniel Cudmore. His roles were small, but he had extended cameos in X2, X-Men: The Last Stand and X-Men: Days Of Future Past. When the comic book movie genre was in the doldrums post-Batman & Robin, the idea of Colossus appearing in five big screen films would have been completely unthinkable. But it happened. Ain't life grand sometimes?

1 BLACK PANTHER

MCU's Black Panther in the daytime

As far back as 1992, actor Wesley Snipes made public his desire to make a Black Panther movie. He felt that Africa had been portrayed poorly in mainstream Hollywood fare and wanted to show the majesty of the continent. His noble intentions unfortunately amounted to nothing after years of development hell, with people routinely believing the movie was about civil rights activists known as the Black Panther Party.

Snipes eventually played Blade instead. Fans then thought the idea of a mega-budget blockbuster being made with a predominantly black cast was impossible. But, in February 2018 Black Panther finally hit the big screen and became a genuine cultural phenomenon. It was much more than a superhero movie; it was an important piece of history.