Television

Many actors in the TV series Power is very poorly done and unbelievable. They do not fit the characters and make the entire series crap.

Tori Spelling in 90210. The series sucked arse, but shoe Horning in the directors daughter is just nepotism.

I love how just about everyone below cites movies rather than TV. But theaters are dead now so what's the difference?

I have one: In the extremely mediocre Sahara (the 2005 adaptation of a Clive Cussler novel and why Clive Cussler never again allowed one of his books to be made into a movie) Steve Zahn cast as the "Burly little Italian" Al Giordino.

Almost every actor cast in Borderlands.

They got a funny man to play the straight man. A woman almost twice the age of Lilith in the game to play Lilith. Jack Black as Claptrap at least makes some sense, but it's not his usual energy and then they tweaked his voice so much I can't tell it's him from clips I've seen.

Chevy Chase as Pierce on Community.

It's debatably a perfect casting because the charcter is a rich, arrogant, racist, sexist out of touch ass... and so is Chevy. He did excellent in the role and was hilarious more often than not. But because he is such a PoS who wasn't really acting, the cast, writers and crew all hated working with him and then he became a very clear burden on the entire show. Resulting in him being semi killed off, but kept appearing in convulated ways? It would've been better for everyone if he was recast right from the start.

Anything Mark Wahlberg is in. I've never seen him do a good performance, and I've seen him do a LOT of terrible ones. Mediocre is the best he's got. And yet, he is sure he's going to get an Oscar one day.

I don't see how all the responses aren't Anthony Mackie in altered carbon s2.

Dane DeHan in Valerean. The part was for an older Han Solo type. Dane was 35, but could still pass for a high schooler. The movie mostly now gets remembered for this miscast, and for its immensely interesting opening sequence, but the whole movie is made of action set pieces made out of sci fi insanity It should be remembered for that, and that Luc Besson is a grooming creepazoid.

Also, Timothy Chalamet. He was terrible in Dune, but I think he was most miscast as Willy Wonka. Hes always wooden, but Wonka needs to be animated! Cinema was introduced to the character with a fake fall into a back flip! Jeremy Alan White is right there!

Anything played by Ezra Miller.

[off topic?]

One of the things that annoys me the most is when the heroes go into a dingy greasy spoon diner in the middle of nowhere and the waitress looks like a cover model. And then, because it costs more if the actress has lines, the heroes don't even interact with her.