The Murderers are Among Us (1946)

  This was literally the first German film made after the fall of the Nazi regime.  Wolfgang Staudte, the writer and director, began working on it while World War II was still going on, then shopped it to the four Allied powers that occupied Berlin:  the British, the French, the Americans, and the Soviets.  Everybody told him no except for the Soviets, who had him change the ending because they were afraid it would provoke vigilante justice in the streets.  Ergo, the ending is a little unsatisfying because who doesn't love vigilante justice but it's understandable.

Susanne (Hildegard Knef) returns to Berlin after supposed internment in a concentration camp only to find that her apartment is occupied by Dr. Hans Mertens (Ernst Wilhelm Borchert), a drunk former soldier who has no intention of leaving.  What starts as an uneasy truce becomes permanent living arrangements as Susanne tries to establish order in both of their lives.  When she accidentally discovers a letter to Hans' former commanding officer's wife, she thinks she is doing Hans a favor by delivering it.  However, by revealing that Captain Brueckner (Arno Paulsen) is actually alive, Susanne inadvertently sends Hans into a tailspin of PTSD and guilt over an unreported war crime.

I say supposed internment above because the narrative does not focus on Susanne at all, despite all evidence that she is supposed to be the main character.  It feels a little like a bait and switch but by the time you get to the end, you won't care because you'll be so angry.  Or maybe not.  Maybe you're more rational than I am and you don't believe in killing Nazis/war criminals on sight.  How nice for you.

The other notable thing about this film is that parts of it were shot in the actual bombed out streets of Berlin so if you wanted to know what a war zone looks like after the fact, you can find out.