In the Cloudman chapter, when you have to kill Ulmeyda once he's turned into a Smile. It's the text at the end that stings the most: "The day when he stops smiling is the day we remember his smile."
Right at the end of the game, when Garcian finally realizes that he's the only real member of the Killer 7, and he's killed all the other members in a previous life. He breaks down, and opens his case to find all the other guns of the other Killer 7 members in it. Meanwhile, a very sad ambient song starts to play while Garcian just says "No! It... it wasn't me! It's all a big misunderstanding!"