As for two different characters in the MCU, there aren't so many: Aren't so many in significant roles that is.
For an extensive list including all the unnamed background characters, see here .
I've chosen to focus just on the characters with memorable roles who I can find pictures of.
Laura Haddock plays Peter Quill's mother, Meredith Quill ( Guardians of the Galaxy ), as well as a female fan of Captain America in the 1940's ( Captain America: The First Avenger ).
Damion Poitier played as Thanos ( The Avengers ) and also plays one of Crossbones Henchmen ( Captain America: Civil War ).
The twin sisters Imogen and Isabella Poynton play Rhomann Dey's Daughter ( Guardians of the Galaxy ) as well as Lila Barton ( Avengers: Age of Ultron ).
Nathan Fillion plays Monstrous Inmate ( Guardians of the Galaxy ) as well as Simon Williams/Wonderman ( Guardians of the Galaxy Vol.
2 deleted scene).
Douglas Robson plays the Horned Marauder ( Thor: The Dark World ) as well as the dark elf in The Collector's museum ( Guardians of the Galaxy ).
Seth Green plays Howard the Duck ( Guardians of the Galaxy ) as well as Expo Fan ( Iron Man 2 ).
Joe Russo plays S.H.I.E.L.D. surgeon
Dr. Fine ( Captain America: The Winter Soldier ) as well as psychiatrist Theo Broussard ( Captain America: Civil War ).
Benedict Cumberbatch plays Stephen Strange ( Doctor Strange ) as well as Dormammu ( Doctor Strange ).
Taika Waititi plays Korg ( Thor Ragnarok ) as well as the right head of Haju ( Thor Ragnarok ).
Stephen Blackehart plays the Knowhere Dispatcher that Drax incapacitates ( Guardians of the Galaxy ) as well as Brahl ( Guardians of the Galaxy Vol. 2 ).
Clem
So plays a Kyln Prisoner ( Guardians of the Galaxy ) as well as a Kamar-Taj Disciple ( Doctor Strange ).
(Though I can imagine these being the same character.)
Kenneth Choi plays Howling Commando Jim Morita ( Captain America: The First Avenger ) as well as his grandson Principal Morita ( Spider-Man: Homecoming ).
Martin Starr plays a student at Culver University (identified in the novelization as Amadeus Cho)
( The Incredible Hulk ) as well as science teacher
Mr. Harrington ( Spider-Man: Homecoming ).
(Ignoring the novelization, I can can see these being the same character.)
Gemma Chan plays Minn-Erva ( Captain Marvel ) and will play Sersi ( The Eternals ).
Enver Gjokaj plays Officer Saunders ( The Avengers ) as well as SSR agent Daniel Sousa ( Agent Carter ).
Bridger Zadina plays bully E.J. ( Iron Man 3 deleted scenes) as well as Mordis ( Inhumans ).
Tony Curran plays Bor ( Thor: The Dark World ) as well as Finn Cooley ( Daredevil ).
Matt Gerald plays White Power Dave ( All Hail the King ) as well as Melvin Potter/Gladiator ( Daredevil ).
Alfre Woodard plays Mariah Dillard ( Luke Cage ) as well as Miriam Sharpe ( Captain America: Civil War ).
Rob Mars plays an hospital orderly who tried restraining Thor ( Thor ) as well as muscle-for-hire Jerome Zandow ( Agent Carter ).
Tom Virtue played Thomas Richards, a Roxxon accountant executed by the Mandarin ( Iron Man 3 ) as well as a motel clerk ( Agents of S.H.I.E.L.D. ).
Clancy Brown plays Surtur ( Thor: Ragnarok ) as well as Ray Schoonover/
The Blacksmith ( Daredevil ).
There also are the people who cameo as different roles.
(e.g. Stan Lee) Outside of the MCU, there are a lot, for example:
Ryan Reynolds plays Deadpool in the 2016 movie Deadpool , as well as playing whoever this is supposed to be in X-Men Origins:
Wolverine : Also check out this great video by Mr. Sunday Movies.
(Although they're not all Marvel roles.)
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Chris Evans played Johnny Storm (AKA Human Torch) and Captain America.
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Ray Stevenson is the Punisher in Punisher: War Zone and Thor's Tight Buddy as Volstagg in Thor.
Volstagg
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Ryan Reynolds plays both Deadpool and Hannibal King from Blade: Trinity . Also (half-jokingly), Stan Lee has played a character in many of the Marvel movies dating back to X-Men in 2000.
Some samples are in the image below.
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Ben Foster plays both Spacker Dave in The Punisher (2004) and Angel in X-Men: The Last Stand .
Spacker Dave Angel
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Enver Gjokaj plays a cop in the first Avengers film and Agent Sousa in the Agent Carter TV show.
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Thinking laterally here, in any of the X-Men movies featuring Mystique, you'll find that several actors play her role in addition to their regular part in the same film - every time she disguises herself as one of the other characters.
scifi.stackexchange.com/users/19533/Darrel Hoffman
Somewhat trivially, there is Patton Oswalt, who has had four different roles (Billy Koenig, Sam Koenig, Eric Koenig, and Thurston Koenig) on Agents of S.H.E.I.L.D.
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Has a single actor ever played two separate characters from the Marvel universe? If so, who?
Has one actor ever played two different characters from Marvel?
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<marvel><actors>
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There are many, many instances of a single actor playing more than one character in the marvel universe. However, most of them include playing background or unnamed characters, rather than both parts being signficant lead roles. One example would be Damion Poitier playing Thanos in the The Avengers and a Henchmen in Captain America: Civil War. Another example would be Seth Green playing Howard the Duck in Guardians of the Galaxy and an Expo Fan in Iron Man 2. Yes - a large number of actors have been identified who have played more than one role from the Marvel Universe. Just to quote one example: : Laura Haddock plays Peter Quill's mother, Meredith Quill ( Guardians of the Galaxy ), as well as a female fan of Captain America in the 1940's ( Captain America: The First Avenger ).
Yes - there are many actors who play more than one role from the Marvel Universe. Numerous examples are provided, covering both more and less memorable roles.