The film was utterly compelling. But the main character was anything but likable. In fact, I imagine even 10 minutes in her company would have me itching to slap her. Yet in the context of the film, I couldn't drag my eyes from the screen.
Why? It all made sense. Everything that motivated her to do the things she did rang true. Even when the things she was doing began to make less and less sense from a rational point of view, they made perfect sense from a character point of view.
And I think that is the key to writing an unlikable character that doesn't turn the reader off. It's hard.
In Chasing the Taillights, one of my critique partners pointed out that Lucy is unlikable for a large chunk of the novel. It hadn't even occurred to me that she could be seen that way, but as soon as it was pointed out, I recognized how her actions could been seen in that light. I struggled to think of ways to change it, to make her more sympathetic, but in the end I didn't. By the end of the book her reasons for acting that way are very clear, and if I'd softened her or changed her in the early part of the book, the impact of the revelations toward the end would have fallen flat. It also wouldn't have been true to the character.
Do you like unlikable characters? What draws you to them?