Having just watched the Alfie remake my nomination would have to be Jude Law. He didn't come across as a charming, charismatic ladies' man. Just a smug twatty man-child. Maybe that's what they were going for? I haven't seen the original so i don't know if Michael Cane portrayed the character differently. I always felt sorry for Cameron Diaz's character in The Holiday being numbered with him too. In my mind he just isn't convincing as a romantic lead.
Who are your most unconvincing actors?