"I am haunted by humans."
The Book Thief p.550
Death is still puzzled by the mystery that is humans. He cannot contemplate how humans can be so cruel and so compassionate at the same time. Liesel's life contains elements of both, and by the end of the novel, Death appears to be no more capable of judging humanity than at the beginning of the novel. Thus, Death tells Liesel that he is "haunted" by humans, just as humans are haunted by Death.