Michelle Dockery - no facial expression at all beyond the odd raised eyebrow (learned at The Sir Roger Moore Acting Academy), and that fake deep voice she puts on in Downton Abbey left no room for any modulation or emotion at all.
Dan Stevens was absolutely rotten in Downton too. His walking stick outshone him in the few episodes it was required, and totally deserved a Best Supporting Actor nod at the BAFTAs in every single way.
Kristen Stewart’s repertoire is entirely composed of mouth breathing and blinking.
Nicole Kidman seems to believe that whispering is a substitute for acting. She’s another one who can’t ever keep her gob closed.
Agree with everyone who’s mentioned the Harry Potter trifecta of tripe. Mind you, I’ve only ever seen the first one, as I couldn’t be bothered to waste the time to see if they improved as they grew older.
Kevin Costner - all the charisma and screen presence of a shoe.
Orlando Bloom’s pointy ear prosthetics carried him through Lord of the Rings and unbelievably, it’s still his best role.
Keira Knightley is easy on the eye, but has the acting ability of a deckchair. She always just shows her teeth for any direction in the script, and in doing so, resembles a Yorkshire Terrier thinking about biting you.
Nicolas “The Bees” Cage.
Will Ferrell thinks he’s waaaaaay funnier than he actually is.
But for the absolute pinnacle of crapness, it has to be Brigitte Neilson in Red Sonja. A performance so bad, she made Arnie look like F. Murray Abraham. I still watch it every time it’s on, mind.