Robert Downey Jr. Reveals the Two Hardest MCU Characters to Get Right — and Why They Stand Out

Robert Downey Jr. has reflected on his long run in the Marvel Cinematic Universe and pointed to two characters he believes were the hardest to properly bring to the screen. In an interview with CBR, Downey discussed the creative challenges behind adapting major Marvel heroes for live-action films.

Downey, who first appeared as Tony Stark in 2008’s Iron Man, became one of the central figures of the MCU and helped launch the franchise into global success.

His character eventually ended his arc with a major sacrifice in Avengers: Endgame, a moment that closed a key chapter of the series. Despite that ending, Downey is set to return to the MCU in a new role as Victor Von Doom, also known as Doctor Doom, in Avengers: Doomsday, scheduled for release in December 2026.

When asked which Marvel characters were most difficult to adapt from the comics, Downey said two names stood out above the rest. He pointed first to Chris Evans’ Captain America and then to Benedict Cumberbatch’s Doctor Strange.

He explained the challenge behind bringing those roles into a grounded cinematic world, saying: “I still feel like the two hardest characters to pull off was what [Chris] Evans did with Cap. And then, I think, [Benedict] Cumberbatch with Strange was like, ‘Are they really going to?’ Because in the comics, it works. And they were holding these spaces of credibility in the real world, and credibility in the world of magic and sorcery.”

Downey’s comments highlight how difficult it can be to balance comic book concepts with a believable live-action tone. Captain America required a transformation from a more old-fashioned patriotic superhero into a modern emotional lead character who could anchor a massive ensemble franchise. Doctor Strange, on the other hand, brought full magical and multiverse elements into the MCU, something that needed a strong visual and narrative foundation to feel real to audiences.

Chris Evans played Steve Rogers for nearly a decade and became widely accepted as the definitive version of Captain America. Before the MCU role, Evans was mainly known for playing Johnny Storm in Fantastic Four films, which made his casting a risk at the time. However, his performance eventually helped redefine the character for a new generation.

Benedict Cumberbatch’s Doctor Strange also became a key figure in the MCU’s expansion into mysticism and alternate realities. The character’s introduction helped push the franchise beyond its early grounded science-based storytelling and into more abstract and cosmic themes.

Downey also noted that many characters in the MCU came with their own adaptation challenges, including his own Iron Man role, which helped start the entire franchise. However, he focused on Evans and Cumberbatch as standout examples of actors successfully grounding complex comic book figures in a realistic cinematic world.

Avengers: Doomsday is currently set to arrive in theaters on December 18.

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