
After Avengers: Doomsday's release, two actors will have appeared in every single Avengers film within the MCU, but that list will likely grow when some rumored actors are confirmed to be in the movie. Following Avengers: Endgame, many thought a new era of the MCU would be ushered in by Marvel Studios, resulting in future Avengers titles being headlined by new actors. However, that was not entirely the case, as some of the MCU's biggest actors decided to return.
Every MCU Actor Who Will Have Appeared in All Five Avengers Films
Robert Downey Jr.

Technically, only two confirmed actors for Avengers: Doomsday will have been in all five Avengers movies, and Robert Downey Jr. is one of them.
In the first four movies, Downey Jr. played Tony Stark (aka Iron Man), leading the Avengers to defeat everyone from Loki to Ultron to Thanos. In Avengers: Endgame, Tony Stark sacrificed himself to bring down Thanos, leading many to believe that Downey Jr.'s time in the MCU had come to an end.
Fans went wild when Marvel Studios announced that the tenured Avengers actor would be returning in Doomsday as none other than Doctor Doom. Since then, Downey Jr. has fully embraced his role as Doom, even sharing some Doom-centric artwork for a special occasion.
Chris Hemsworth - Thor

The only other actor who has appeared in all the other Avengers films who has technically been "confirmed" for Avengers: Doomsday is Chris Hemsworth.
Unlike Downey Jr., Hemsworth's character survived the events of Avengers: Endgame. Since then, he has even headlined Thor: Love and Thunder, the fourth film in his solo franchise.
Since Avengers: Doomsday began production, Hemsworth has been spotted on set a couple of times. In one behind-the-scenes photo of some of the film's main actors, he could be seen standing beside the likes of Channing Tatum, Simu Liu, and Paul Rudd.
BONUS: Chris Evans

Marvel Studios has not officially announced that Chris Evans will be returning to the MCU for Avengers: Doomsday, but multiple rumors suggest the franchise veteran will have some sort of role in the film.
If Evans does appear, he will join Hemsworth and Downey Jr. as actors who have appeared in all five Avengers movies.
While Evans' involvement has been rumored, many of them also say that the actor will not be returning as Captain America or Steve Rogers. While it is always possible that he could pick up the shield one more time, the latest rumor revealed that Evans could be playing an entirely new character.
BONUS: Mark Ruffalo

Mark Ruffalo is another actor who has not been confirmed to have a role in Avengers: Endgame. However, an industry insider recently reported that Ruffalo would be in the film, which wouldn't be surprising considering his character is still alive in the MCU.
It is also worth noting that Ruffalo's Hulk was featured in some leaked concept art from a couple of months ago. Avengers: Doomsday directors Joe and Anthony Russo claimed the concept art was fake, but many fans aren't convinced.
Even if the art wasn't real, there would be no reason for Ruffalo not to be cast in Doomsday. The actor's last MCU appearance came in Disney+'s She-Hulk, where it was revealed that Hulk had a son, so that will have to be addressed at some point.
BONUS: Samuel L. Jackson

Samuel L. Jackson is yet another actor who doesn't have a confirmed role in Avengers: Doomsday, but his involvement has been reported by industry insiders.
Jackson will return as Nick Fury if those reports are true, meaning he would join the other actors as the only names to have been in every single Avengers film.
Even if Fury doesn't play a huge role in Doomsday, it would still only feel right to include him in the movie since he was responsible for forming the original Avengers team.
BONUS: Tom Hiddleston

Unlike the other bonus actors on this list, Tom Hiddleston has actually been confirmed for Avengers: Doomsday and will even play a highly important role.
Technically, Hiddleston hasn't been credited in every Avengers film because he was not in the final cut of Age of Ultron. However, he did film a scene that was going to be put into the sequence where Wanda Maximoff enters Thor's mind. The scene was ultimately deleted, though.
So, Hiddleston may not have technically appeared in every single Avengers film in the final cut, but he did at least film scenes for every installment.