Activity Número One — characters likely to experience the most changes

I think the characters most likely to experience monumental changes throughout the book are Liesel Meminger, Rosa Hubermann and Death himself. Liesel is the central character in the novel, so she was always destined to have the most brutal hardships thrown her way. Even in the first few pages she experiences changes: her brother dies, her mother (essentially) abandons her, she finds a book, she comes to live in Himmel Street with a friendly man and foul-mouthed women, and she makes some new friends. Liesel grows up, she begins to steal, she stops having her nightmares, she does the ironing. The further you get into the book, the more Liesle changes.

Death experiences changes of a completely different kind. At the beginning of the book, we get the impression that Death finds his job dull, a repetition of the same chore every day for eternity. But then he notices Liesel. Death sees her three times before she dies, and each time he takes a special interest in her stories, remembering them, guarding them for her. We see Death become more and more apologetic towards Liesel, although he knows he has no control over the task he has to carry out. 

Rosa Hubermann herself doesn't change, but Death and Liesel's perception of her changes, and that is sort of the same thing. We see her become friendlier and more accommodating to Liesel, dropping the 'saumensch' and the 'arschloch' and began to actually acknowledge Liesel as a real human being.