10 Actors Who Could Ruin Upcoming Movies

10. Robert Downey Jr. - Avengers: Doomsday

Let's kick this list off with perhaps the biggest elephant in the room in Hollywood right now - the return of Robert Downey Jr. to the Marvel Cinematic Universe in the now-filming Avengers: Doomsday.

Marvel Studios shocked the world last summer when they announced that Downey would be returning to the franchise not to reprise his role as Iron Man but instead to play the villainous Doctor Doom.

Tellingly, Marvel have remained tight-lipped about precisely how this will work, leaving fans to speculate on whether Downey's Doctor Doom might be a Tony Stark variant, or more bewilderingly, Downey could be genuinely playing an entirely new character with no link whatsoever to Tony Stark.

Either way, the bombshell announcement proved immediately polarising, some relishing the opportunity to see Downey back in the MCU, while others saw it as a wildly desperate move on Marvel's part - an "in case of emergency, smash glass" moment to try and restore the MCU's floundering goodwill of recent years.

We can only hope that the Russo brothers are cooking up something interesting and unexpected here, though it's also quite possible that Downey ends up being an albatross hanging around the movie's neck.

There's no doubt he'll give it his all as usual, but on a storytelling level, will his presence be anything more than cynical stunt casting?