Beyond the German's penchant for casual brutality (more pronounced in the East) and collective reprisals, German military occupation financially was highly exploitative. The Third Reich feared so many young men under arms would create inflation of the Reichsmark, so German troops occupying foreign countries were paid in the currency of that state. So Germans in France were paid in Francs, the General Government zloty, etc via Reichskreditkassenscheinen (Reich Credit Bank Slips/RKK). RKKs were paper slips could not circulate in the Reich but could be exchanged at local banks for currency. The occupation authorities often pegged the conversion of RM to occupation money at artificially high levels, so a German landser stationed in France arguably received more pay than his equivalent in the Reich. German soldiers naturally went on spending sprees and shipped much of these foreign goods home. This fiscal policy, which obviously and intentionally favored Germans, contributed to the overall destruction of occupied Europe's domestic economies. When coupled with the massive expropriations of food and raw materials back to the Reich, this created a larger feeling of desperation in which dealing with German soldiers and other members of the occupation apparatus was a means to survive.

/u/commiespaceinvader 's answer here goes into more depth on the RKKs and their baleful impact on the occupied.