In the boy in the striped pajamas, does Karma hit Bruno's father or not?
I think that the force of Karma hits Bruno's father.
If we define Karma as a person's actions playing a role in their end fate, it becomes clear that the ending of Boyne's novel provides karmic alignment to Bruno's father. Bruno's father was an active participant in Nazism. His support of Nazism causes a rift between he and his mother. It compels him to move his family to Auschwitz. Bruno's father sees participation in Nazism as critical to his career advancement. Bruno's father does not pause to consider the implications of his actions. He refuses to see how his work causes death and suffering to many. He does not acknowledge that what is happening is barbaric and cruel.
Such denial is where Karma becomes evident. When Bruno's mother and father search for him in “every part of the house and...all the local towns and villages,” it is a painfully Karmic element. Bruno's father must experience the loss that millions of parents experienced during the Holocaust. When Bruno's father pieces together what happens, he realizes that his own role in the devastation of millions contributes to the death of his only son. He experiences what he did to many families. His actions play a clear role in his fate. The moment where he stands at the threshold of such revelation is where Karma hits Bruno's father in the most painful of ways.