What are the consequences of seeking revenge in Beowulf?

Beowulf is an epic story of revenge and vengeance. The entire stiory is driven by the character's need to right the wrongs done against them by killing their foes. This cycle of revenge is began by the monster Grendel who is descendant from Cain, the first murderer who killed his brother out of revenge for not being favored by God. Grendel hates the mead hall the Danes have built and their nightly singing partying, thus he takes his revenge by terrorizing the Danes. Beowulf arrives in the kingdom to kill the monster Grendel for attacking the Danes and also seeks to make a greater name for himself through battle. Beowulf mortally wounds Grendel and so the Danes have their revenge. Grendel's mother, however, is so wrought by her son's death that she takes her own revenge by killing the thane and dear friend of the Danish King. This cycle of revenge is ended once Beowulf seeks out Grendel's mother and kills her for her act. The cycle of bloodshed is renewed years later by a thief who steals a piece of treasure in the form of a goblet from a Dragon who had been protecting his great wealth for centuries. The dragon exacts his revenge by burning down the countryside in search of the thief and part of the kingdom of the Danes is destroyed in the carnage. Beowulf is once again called upon to take revenge for the Danes by killing the dragon. The dragon and Beowulf fight and both are killed in battle. In the end, all those that had been involved in the cycle of revenge since the very beginning of the story are dead. Thus is the theme of the story, that all who partake in revenge shall suffer as did all those who fought in the story of Beowulf.