Peace

In 2 Samuel 2 there is conflict between the house of David and the house of Saul. One day there was a fierce battle between the 2. Asahel was chasing Abner. Abner keeps telling him to stop, that he (Abner) doesn't want to hurt him. But he doesn't stop and Abner ends up killing him.
Then Asahel's brothers pursue Abner and Abner again strikes out for peace.

26..."Must the sword devour forever? Don't you realize that this will end in bitterness? How long before you order your men to stop pursuing their brothers?"

This actually works and they stop fighting. But the anger of Asahel's brothers' festers.

In 2 Samuel 3, it tells us that in Hebron David has 6 sons by 6 different women. I guess as king, that's the sort of thing you do.

Then Saul's son accuses Abner of sleeping with Saul's concubine. Now I don't really see what the problem was as Saul was dead, but there must have been some rules and things about who gets whose concubine, or whatever. But the accusation offends Abner and he goes and makes peace with David.

But Asahel's brothers get mad that David has made peace with Abner and they go off and murder him. Either their pain must have been deeper than David's and they were not able to forgive or David had more grace for forgiveness.