Hubris - overwhelming pride. Relationships among kinsmen were the most defining characteristic of Anglo-Saxon tribes. The death of a kinsman had to be avenged. To kill a kinsman was the greatest crime in the Anglo-Saxon society. Cain, a brother-slayer in the Christian Bible, symbolized the worst kind of person. Bravery and boasting was encouraged and rewarded. Unferth, who supposedly was the bravest among Danish people, refuses to fight with Grendel's mother. This is a shameful act, and the author describes him as a coward and a brother-slayer, even though we don't know if he actually killed anyone of his own kin.