Dill is an important character because he adds humor and innocence to the story and also serves as a catalyst for Scout and Jem's coming of age journey.
Edna is an outsider at Grand Isle because she is a non-native to the island and does not conform to the societal expectations of women during that time period.
Frankenstein remains quiet during Justine's trial because he feels guilty for creating the monster who committed the crime and is afraid of being seen as the true culprit.
Hamlet delays killing Claudius because he wants to make sure he is truly guilty of his father's murder and also because he wants to plan the most effective revenge.
Amir doesn't help Hassan in the alley because he feels guilty and ashamed of the incident that led to their friendship being strained in the first place, and fears being exposed as having played a part in it.