Max, like Liesel, comes to the story fresh from experiencing great loss. He feels deeply guilty for leaving his family to save himself, an act he sees as a choice rather than a necessity to survive. He also feels ashamed of the burden he places on the Hubermanns since he knows he’s putting them in serious danger by being in their home. He is often conflicted between his desire to stay alive and his wish to make life easier for the Hubermanns by leaving, but ultimately he knows leaving would likely mean his death. Despite everything, his wish to live is strong, and he fights to stay alive against the cold and malnourishment and illness as he hides out.
In fact, that fighting spirit defines Max’s character to a great degree. As he lives isolated in the Hubermann’s basement, he imagines literally fighting Hitler and countless Germans, and even as he’s pummeled in his imagination he struggles on. We also learn that he used to fight a boy in his neighborhood, and though he rarely won, he never gave up. Later he is led to the labor camp at Dachau, and though we don’t see his experiences there, there’s little doubt that he still had to fight to stay alive. The only time Max seems not to be fighting is when he is with Liesel. In those instances he is suddenly very soft and kind.