One of my favorite performances of Marion’s is her portrayal of Tina Lombardi in “A Very Long Engagement.” (And because I want to appear smart and worldly, here’s the French title: “Un Long Dimanche de Fiançailles.” Yes, cut + paste is a wonderful thing).
Marion has a very short role in this lenghty, WWI film, but she practically steals the show. This particular scene is heartbreaking (if you haven’t seen the film, I wouldn’t recommend watching this particular sequence–it’s a bit spoilerish, especially as it relates to the Lombardi character).
As you probably know, this performance earned Cotillard the César award for Best Supporting Actress. The film itself is pretty magical–worth checking out.
ETA: If you noticed, Tina Lombardi didn’t have any regrets either.
Marion Cotillard's Road to Oscar 