When Noah was told of the flood's coming, he did not pray for mercy on behalf of the world.
When God told Abraham that he was about to assess S'dom and Amorrah, Abraham continually questioned God about the number of righteous citizens it would take to save the city. The number arrived at was 10.
When God told Moses to "let Me alone" so that he could destroy Israel and make Moses a great nation, Moses beseeched Him not to do it, for the sake of keeping His promise to Abraham, Isaac and Israel.
These are three different reactions to news of the destruction of a population. Obviously the circumstances are greatly different in each case, but do we know what core principals lead to each case and each decision?
Abraham was told that 10 righteous citizens were necessary to avoid destruction. Can this rule be transferred to other situations of the like? If it's not always 10, then what is the number based on? Was Moses' argument for keeping the promise enough to save the nation or did Israel also have a required quota of righteous people? Abraham asked "Will You indeed sweep away the righteous with the wicked?" We know that at the very least the Levites were innocent of the crime that angered God. Would He have killed them along with the rest of Israel if Moses hadn't prayed to him?
What do we know about how this works?
What does God's saying "let Me alone" to Moses tell us about the ability of the righteous to influence His judgement?