These characters have made numerous appearances in Marvel movies.
Some Marvel characters appear quite frequently in films. Some, not main characters, still make regular appearances in various Marvel movies.
Below are the 12 characters who have made the most appearances in Marvel movies.
12. Loki

Loki is a recurring character in the MCU. He has appeared in Thor, The Avengers, Thor: The Dark World, Thor: Ragnarok, Avengers: Infinity War. Additionally, Loki variants appear in Avengers: Endgame and the Loki series. The Loki series has introduced numerous Loki variants portrayed by different actors.
Actor Tom Hiddleston voices Loki in three episodes of What If?.
11. Wong

Before Phase 4, Wong appeared in Doctor Strange, Avengers: Infinity War, and Avengers: Endgame. Suddenly in Phase 4, Wong seems to be everywhere.
He graced Shang-Chi, Spider-Man: No Way Home, and Doctor Strange in the Multiverse of Madness. Wong also appears in some episodes of What If? (voiced by Benedict Wong) and is confirmed to appear in She-Hulk.
10. Pepper Potts

Pepper has appeared in Iron Man, Iron Man 2, Avengers, Iron Man 3, Spider-Man: Homecoming, Avengers: Infinity War, and Avengers: Endgame.
Pepper also appears in episode 6 of What If? and makes a fleeting appearance in What If? episode 9. However, this version of Pepper is voiced by Beth Hoyt, not by Gwyneth Paltrow.
9. Bucky Barnes

Bucky Barnes has appeared in Captain America: The First Avenger, Captain America: The Winter Soldier, Ant-Man, Captain America: Civil War, Black Panther, Avengers: Infinity War, Avengers: Endgame, and later in The Falcon and the Winter Soldier series.
Additionally, he is prominently featured in two episodes of What If?. Sebastian Stan continues to voice the character Bucky in these episodes.
8. Thor Odinson

Thor has appeared in Thor, The Avengers, Thor: The Dark World, Avengers: Age of Ultron, Doctor Strange, Thor: Ragnarok, Avengers: Infinity War, Avengers: Endgame. He will also make a return in the upcoming film Thor: Love and Thunder.
Additionally, some variations of Thor have been featured in What If?. Interestingly, the Thor variant in What If? is still voiced by Chris Hemsworth.
7. Natasha Romanoff

Natasha Romanoff is a recurring character in the MCU. She first appeared in Iron Man 2, followed by The Avengers, Captain America: The Winter Soldier, Avengers: Age of Ultron, Captain America: Civil War, Avengers: Infinity War, Captain Marvel, Avengers: Endgame, and finally Black Widow.
Some variations of Natasha are also highlighted in What If? and voiced by Lake Bell.
6. James Rhodes

The actor for the character Rhodey has been changed. He first appeared in Iron Man, portrayed by Terrence Howard. Then, starting from Iron Man 2, the role was taken over by Don Cheadle.
Later on, Rhodey appears in Iron Man 3, Avengers: Age of Ultron, Captain America: Civil War, Avengers: Infinity War, Captain Marvel, Avengers: Endgame.
Rhodey also makes a guest appearance in episode 1 of The Falcon and The Winter Soldier. Additionally, he has been confirmed to appear in Armor Wars. He also appeared in episode 6 of What If?, voiced by Don Cheadle.
5. Hulk

In the MCU, Hulk has been portrayed by different actors. In The Incredible Hulk, Bruce Banner was played by Edward Norton. Then, starting from Avengers, Mark Ruffalo took over the role.
Later, Banner appeared in Iron Man 3, Avengers: Age of Ultron, Thor: Ragnarok, Avengers: Infinity War, Captain Marvel, Avengers: Endgame, and Shang-Chi.
Mark Ruffalo also voices Bruce Banner in some episodes of What If?. In the future, Banner will return in She-Hulk.
4. Steve Rogers

Steve Rogers has appeared in Captain America: The First Avenger, Captain America: The Winter Soldier, Avengers: Age of Ultron, Ant-Man (in the post-credits scene showing Steve and Sam finding Bucky), Captain America: Civil War, Spider-Man: Homecoming, Avengers: Infinity War, Captain Marvel, Avengers: Endgame.
Later on... Chris Evans also appeared in Thor: The Dark World, but that was Loki disguised as him, not the real Steve Rogers.
Variations of Steve Rogers also appear in What If?, although they are not voiced by Chris Evans. Josh Keaton voices Rogers in What If?.
3. Tony Stark

Tony Stark, portrayed by Robert Downey Jr., frequently appears from Phase 1 to Phase 3.
He appears in Iron Man, makes a cameo in The Incredible Hulk, Iron Man 2, The Avengers, Iron Man 3, Avengers: Age of Ultron, Captain America: Civil War, Spider-Man: Homecoming, Avengers: Infinity War, and Avengers: Endgame.
This series of appearances by Tony Stark makes him feel like the central character from Phase 1 to Phase 3.
Variations of Tony Stark are also highlighted in What If?, but they are not voiced by Robert Downey Jr. Tony is voiced by Mick Wingert in What If?.
2. Nick Fury

Throughout Phase 1 to Phase 3, Nick Fury appears quite frequently. He appears in Iron Man, Iron Man 2, Thor, Captain America: The First Avenger, The Avengers, Captain America: The Winter Soldier, Avengers: Age of Ultron, Avengers: Infinity War, Captain Marvel, Avengers: Endgame, Spider-Man: Far From Home. He also made appearances in both episodes of Agents of SHIELD.
Although in some films he only has cameo roles, Nick Fury clearly remains a consistent presence from Phase 1 to Phase 3.
Now, because Fury is still alive, he will also appear in Phase 4. Variations of Fury appear in What If?, all voiced by Samuel L. Jackson. He is then confirmed to appear in Secret Invasion. Not only that, according to Samuel L. Jackson, Fury will also appear in The Marvels.
1. Information Seeker (Stan Lee)

Stan Lee has played numerous cameo roles in MCU films. In fact, he not only appeared in MCU films but also in previous X-Men and Spider-Man films.
After the MCU era began, Stan Lee appeared from Iron Man to Avengers: Endgame.