I have noticed a pattern in many of the books I read. The authors depend on human weakness rather than strength to drive their stories. They count on sinfulness rather than saintliness to provide conflict and establish a basis for the plot. What would happen to plot if there was no conflict? And from where would conflict arise if there were no evil? As much as we humans long for a heavenly paradise, we read stories about hell.
Consider The Iliad by Homer. The entire narrative is based on the frailty of human nature, from Discord's golden apple to the Trojan's gullibility in accepting a parting "gift" from the Greeks. A prime example of using weakness rather than strength is found in the character of Achilles. Although he is the greatest warrior among them, Homer uses his resentment to enhance the action. Achilles probably could have returned Helen to Menelaus soon after the Greeks landed at Troy. But then there is no epic story. Instead, Homer has Achilles sulk in his tent because Agamemnon stole his prize. It is Achilles' weakness rather than his strength that provides the drama. It also provides a lull in the action so that Hector can have that poignant conversation with Andromache.
The power of human frailty is evident in other works of literature. Without Kurtz' descent into "the horror", there would have been no journey for Marlowe into the heart of darkness. If Mr. Bennet had been energetic, prudent, and willing "to enlarge the mind of his wife", Elizabeth might not have ever married Mr. Darcy. Indeed, without Darcy's pride and Elizabeth's prejudice, where would the story be? Rewrite Bertie Wooster's character so that he is no longer a well-meaning but silly ass, and there would be no need for Jeeves to rescue him.
It is interesting to analyze works of fiction and determine the particular sin that the writer depends on for the story. A fatal flaw could even be a character's perfection. If someone thinks he or she never makes a mistake, they have just set up a conflict.