The major weakness of Hans Hubermann is the way that he is shown to be too good, kind and compassionate. This may not sound like a weakness to you, but let us remember that against the backdrop of Nazi Germany and its inhumanity in so many different forms, being good and kind can be a positive death sentence. Of course, for Hans Hubermann, it nearly is. Consider how in Part 7 Hans is overwhelmed by the sight of starving Jews walking through the streets. Note how he responds:

The Jew stood before him, expecting another handful of derision, but he watched with everyone else as Hans Hubermann held his hand out and presented a piece of bread, like magic.

This "futile miracle" as it is described shows the compassion of Hans, but it also shows how this sense of goodness gets both him and those around him into trouble. This act after all causes the Jew that is given the bread to get whipped. Hans himself is similarly punished and of course Max, the hidden Jew in the Hubermann basement, is forced to leave the safety of this house because of this act of goodness.