Amy and her daughter (spoilers)
So I watched this movie last night, and around this board I've noticed only one person really mention Amy's fate tied in with her backstory.
She passes on 2 minutes in the barrel, which shepard knew she would do. So he sticks her with 4 minutes. He mentions to her that she watched her daughter drown in a bathtub at the hands of the father.
Of any death in the film, this is the only one that felt like sweet justice.
shepard was an evil basket-case, but I do applaud him for avenging a child's murder, to the one who was supposed to protect that child, in the same slow painful death that her daughter endured.