There’s a good book called “Ordinary Men: Reserve Police Battalion 101 and the Final Solution in Poland” by Christopher Browning which explores this. The Reserve Police Battalions were created by Germany to police captured territory, but they were seen by ordinary Germans as a way to avoid the war and conscription. The members were not Nazis, and almost to a man they joined because it was an honorable way to avoid participating in the evils happening all around them. They were only trained for ordinary honest police work, but in the end many of them were being used to hunt down and murder Jews. They were sent out into forests to comb them for underground shelters. They rounded up Jews and herded them into mass graves.

Almost none of them complained or tried to avoid participating. No one punished them if they didn’t participate. No one coerced them into participating. A few asked for and received transfers, if I recall correctly. The best that can be said about the rest is that many of them are believed not to have actually fired their weapons. Some of them probably went the whole war without actually killing anyone, technically. They were just assigned the job so they did it.