Nazis

Nazis are the German regime, led under Adolph Hitler during WWII and were an oppressive force.
Some may have their own fears of Nazis due to a family history or learning about them as children. In the case that the fear is fact based because of a interacting with the Nazis then the dream itself may not be representative. For the part of the population that were not directly affected by the Nazis, they can still be a scary group. If you dream about them then your psyche is trying to send you a direct message.