Ralph Fiennes as John Steed was a disaster in the "Avengers" movie. In fact, I googled "bad casting" and that was high in the results. Also the Batman movies. Michael Keaton as Batman? Val Kilmer as Batman? Come to think of it, Tobey McGuire as Spiderman?
Jodie Foster in "Maverick?" Leo DiCaprio as Howard Hughes? Tom Hanks as Tom Wolfe's "master of the universe" in "Bonfire of the Vanities." Or Bruce Willis as and unscrupulous tabloid journalist in the same movie? Adam Sandler in just about anything?
Good selections for terrible miscasts all!