Comic book movies can often be quite contentious when it comes to casting, with fan uproar frequently being unleashed on up-and-coming superhero actors despite only sometimes being justified. The reception of a casting announcement can have big implications on the success of a given comic book movie, sometimes riding on a single amazing superhero casting. Public outcry from fans can sometimes be indicative of a poor performance, but in many cases, hesitations about certain actors stepping into comic book roles end up being completely unfounded.

Actors can be considered unfit for superhero roles for a variety of different reasons. Some casting choices could see actors playing against type, or entering a big-budget superhero film despite little to no experience in blockbusters or action movies. Regardless of whether or not their gambles end up paying off, movie studios often take huge risks with controversial casting decisions for their valuable comic book IPs.

10 Heath Ledger's Joker

The Dark Knight

It's hard to imagine a performance as critically-praised as Heath Ledger's Joker ever being in question with the hindsight of the final result. Heath Ledger's chilling take on the Clown Prince of Crime is easily the best live-action Joker, at once being funny, frightening, and delightfully unhinged.

Earning Ledger an Academy Award, there are few superhero performances as gregariously successful as his take on The Joker, drawing iration from even the highest-brow of prestige cinema critics. That being said, Heath Ledger was far from a popular casting decision before the film was released.

It's important to realize that Heath Ledger was better known for being a romantic heartthrob on-screen in films like Brokeback Mountain, Candy, and 10 Things I Hate About You. Luckily, Christopher Nolan took a chance on the actor for the second installment in his trilogy, resulting in one of the greatest cinematic villain performances of all time.

9 Robert Downey Jr.'s Iron Man

Iron Man

Another legendary comic book movie performance that is difficult to imagine as being controversial today, the decision to cast Robert Downey Jr. as Iron Man wasn't an easy one for Marvel Studios. In 2008, Robert Downey Jr. had enjoyed a handful of critical successes, but wasn't thought of as a franchise-carrying leading man, better known as a member of the so-called "Brat Pack" for coming-of-age films like Weird Science and Back to School. Not only that, but the tumultuous and very public woes in his private life presented something of a PR risk to Marvel's brand.

However, Robert Downey Jr. knocked it out of the park as Tony Stark, using his experience to craft a snarky, yet lovable persona that would carry the MCU for years to come. If it weren't for his casting in Iron Man, it's impossible to say if the franchise would've ever grown into the industry giant it is today. It's a good thing John Favreau's vision for Iron Man included Robert Downey Jr.

8 Jared Leto's Joker

Suicide Squad

Another cinematic Joker, Jared Leto was another controversial contender, especially as the next live-action performer to follow up Heath Ledger's brilliant version of the character. Even today, Jared Leto is best known for his work in meditative dramas like Dallas Buyers Club and dark cult films like Fight Club or American Psycho. Adding fuel to the fire was the poorly-received first look at his Joker makeup, which many fans criticized for its hilarious over-the-top edginess, not to mention Leto's bizarre behavior to his Suicide Squad co-stars while method acting as The Joker.

Largely edited out of the story of Suicide Squad, Jared Leto's Joker came across as weird and off-putting rather than intimidating or cool. In this case, critical backlash towards the casting persisted after the release of the film, disparaging Leto's quirky mannerisms as trying too hard. Even if he got a brief scene to redeem his performance in Zack Snyder's Justice League, Jared Leto certainly didn't leave behind a strong legacy as The Joker in the DCEU.

7 Jesse Eisenberg's Lex Luthor

Batman v Superman: Dawn of Justice

Jared Leto's Joker wasn't the only DCEU villain to have fallen short of already low audience expectations. Jesse Eisenberg was met with incredulity upon being cast as Lex Luthor, Superman's infamous corporate nemesis. This was widely thanks to his ubiquity as nebbish or soft-spoken nerd characters, with his roles in movies like Zombieland or The Social Network falling far outside the realm of personality typically associated with the ruthless supervillain.

Upon the release of Batman v Superman: Dawn of Justice, many fears about Eisenberg's take on the character were soon justified. Rather than a smooth, controlling CEO, Lex Luthor was a quirky millennial brat prone to lengthy tirades about gods and men. Eisenberg didn't even shave his head for the role in Batman v Superman: Dawn of Justice, showing a contempt for a DC antagonist not seen since Cesar Romero refused to shave his mustache for The Joker in Adam West's Batman. In the end, Eisenberg's Lex Luthor was more like a cartoonishly evil version of his Mark Zuckerberg performance.

6 Ben Affleck's Batman

Batman v Superman: Dawn of Justice

Indeed, Batman v Superman: Dawn of Justice was a film rife with controversial casting choices. Ben Affleck's Batman casting raised many eyebrows considering the ill fate of his last outing as a cowl-wearing superhero in the critically reviled Daredevil. Even if Affleck had outlived his public perception from Gigli, few were hopeful that his second attempt at portraying a crime-fighting vigilante was going to go well.

Shockingly, Ben Affleck wasn't half bad as Batman, presenting a unique take on an older, more weathered Dark Knight that had a ferocious willingness to kill not seen in other live-action Batmen. He may not have become the most beloved actor to ever don the iconic cape and cowl, but he certainly held his own in an otherwise flailing superhero film, providing a gritty humanity to the action. For all the problems the DCEU may have had, Ben Affleck as Batman certainly wasn't one of them, doing the best he could with the limiting material he was handed.

5 Michael Keaton's Batman

Batman (1989)

Ben Affleck isn't the only Hollywood A-lister to be a shocking choice for the role of Batman. Tim Burton's Batman promised to re-invent the character in the eyes of the public, stepping away from the campy fun of the Adam West version and taking a darker tone more reminiscent of the actual comics. This was a confusing goal for some when paired with the casting of Michael Keaton as Batman, considering that Keaton was a comedy darling best known for movies like Mr. Mom and Night Shift - A far cry from the dark vigilante that was promised.

Of course, Micheal Keaton's original take on a comic-accurate Batman is still one of the greatest to this day. Even decades later, Michael Keaton's Batman is a cinematic icon, proven by his recent return to the role in 2023's The Flash. While he still carried echoes of his comedic chops as Batman, particularly when moonlighting as Bruce Wayne, Micheal Keaton proved he could get serious as the Caped Crusader.

4 Zendaya's M.J.

Spider-Man: Homecoming

It's hard to understate just how highly-anticipated Tom Holland's first solo Spider-Man movie was coming off of the warm reception to his introduction to the MCU in Captain America: Civil War. It's no wonder those closely following the comic book movie news circuit were alarmed to see Zendaya of Disney Channel fame cast as "M.J.", ostensibly referring to Mary Jane, Spider-Man's classic love interest. Many complained that Zendaya didn't have the look for Mary Jane, usually portrayed as a fiery, outspoken redhead with a heart of gold.

Hilariously, the Marvel Cinematic Universe flipped the script on the fan outrage by revealing that "M.J." wasn't Mary Jane, but Michelle Jones, an original play on Peter Parker's typical romantic partner. Zendaya's skill in the role soon made the question of her actual name a moot point anyway, instantly creating a chemistry with Spider-Man that bled into real life with the eventual blossoming of Zendaya and Tom Holland's relationship. It's hard to even the initial controversy in the wake of Zendaya's ubiquity with the character.

3 Michael Clarke Duncan's Kingpin

Daredevil

While the controversy over Zendaya's race was able to be hidden in the insistence that Mary Jane should be a redhead, the same couldn't be said for Michael Clarke Duncan's casting as Wilson Fisk, a.k.a. Kingpin, in 2003's Daredevil. The idea of race-swapping characters was far less accepted in the early 2000s, with no small amount of contention arriving from the fact that Michael Clarke Duncan's ethnicity didn't match Kingpin's in the comics. Not only that, but Duncan was better known as a gentle giant in The Green Mile, making for a hard sell as a ruthless gangster.

2003's Daredevil had a lot of problems, but Michael Clarke Duncan's Kingpin performance certainly wasn't one of them. The actor's massive stature and intimidating aura worked wonders up against Ben Affleck's Matt Murdock, standing out as a positive despite the film's best attempts. Even if he has since been outshone by Vincent D'Onofrio, Michael Clarke Duncan deserves more credit as an intimidating and grounded comic book villain.

2 Topher Grace's Venom

Spider-Man 3

Of the three villains occupying the busy cast of Sam Raimi's Spider-Man 3, Venom was by far the most hotly-anticipated. However, the decision to cast Topher Grace, of all people, as Eddie Brock was one that befuddled even the most die-hard fans of the films up to that point. Topher Grace was, and still unfortunately is, best known from That '70s Show, where his character has far from a threatening persona.

Sadly, the reluctance to accept Grace as one of Spider-Man's most important villains was soon proven to be well-founded. Topher Grace's silly, envious jock was far from the comic-accurate Eddie Brock Venom hopefuls were waiting for, leaving much to be desired as perhaps the single weakest villain of the three antagonists making up Spider-Man 3. With Tom Hardy's take on the lethal protector in his own movie trilogy, there's no comparison between the two live-action Venoms in of quality.

1 Mark Ruffalo's The Hulk

The Avengers

The nascent Marvel Cinematic Universe found themselves in a sticky situation when it came to Edward Norton dropping out as Bruce Banner, a.k.a. The Hulk, following the release of 2008's The Incredible Hulk. With only vague creative differences being cited as the reason behind Norton's exit, winning over new fans with a recast wouldn't be an easy task. That went doubly so for Mark Ruffalo, whose casting announcement prompted confusion as the actor had only been an indie darling in movies like Eternal Sunshine of the Spotless Mind and The Kids Are Alright.

Despite his lack of blockbuster experience, Ruffalo was more than able to hold his own against the stacked cast of The Avengers, fitting in perfectly as the quiet scientist amid a team of loud eccentrics. MCU viewers soon grew accustomed to Ruffalo's emotional proficiency and affinity for Dad humor, leaving a lasting impression as a worthy founding Avenger. Even if later comic book movies in the MCU turned the Hulk into more of a ing goofball, Ruffalo's performance still remains well-received.