Worst: The forest scene (Twilight)
From the comments on YouTube, I gather that the forest scene in Twilight, where Bella calls him on being a vampire, is a lot of people's favourite scene. I can see the romanticism of it, but there are so many ridiculous elements that it comes off as laughable. First there is Edward's super-fast running while carrying Bella on his back like a little girl (thanks to YouTuber ASmilingMalice for that observation). Then there is Edward's sparkling skin. "That's like diamonds," Bella says. Thank you for stating the obvious! But the worst is Edward's rationale for his obsession with Bella: "You're like my own personal brand of heroin," referring to his desire to drink her blood. Worst line of dialogue ever.