10. Topher Grace - Spider-Man 3
You need only take a passing glimpse at the Spider-Man comics to know that Eddie Brock has a square jaw and is supposed to be, above all else, a man's man; athletic and tough. That is not Topher Grace, who ended up being cast as Brock/Venom in Sam Raimi's much maligned third entry into the popular comic book series. While Grace is a fine actor in his own right, he's just completely wrong for the role of Brock, lacking the physical presence needed to make either of the two roles work; the guy played Eric Foreman on That 70's Show, for God's sake! While as Venom he gets the psychopathic elements of the character down pat, it's the look that's all wrong; seeing Grace's boyish face wrapped around a CGI venom "suit" looks frankly ridiculous. A more mature-looking actor was desperately needed for the role, and sadly this is one case of rabid fanboy scepticism actually being justified by the underwhelming end result, which angered comic book geeks the world over (along with everything else in that film).