In Khaled Hosseini's novel The Kite Runner, Amir is haunted by a childhood decision, which ends up motivating many of his adult decisions. This decision was, as your question noted, an inaction rather than an action.
When Amir is a young boy, he witnesses the rape of Hassan, a boy whose relationship with Amir is essentially that of servant. Amir does not interrupt the crime, nor does he choose to share it with anyone. In fact, in his guilt, he turns on Hassan, treating him cruelly, never apologizing for his inactive role in the situation.
It is later revealed that Hassan was actually Amir's half-brother, which exacerbates Amir's horrible feelings of guilt. However, in the end, Amir is able to redeem himself for his inaction during his childhood.