The battle between Beowulf and Grendel is long, brutal, and bloody. It was always expected that the great showdown between the Geatish warrior and the hideous bloodthirsty monster would be like this. After all, there's something not of this world about Grendel, and so it would always take something a bit special to defeat him.
Enter Beowulf, the proud Geatish warrior. He doesn't flinch when Grendel attacks him and tries to devour him as he's done with countless Danish warriors in the past. When Grendel grabs Beowulf by the arm, our hero keeps his cool. Instead of trying to extricate himself from the creature's fearsome grasp, Beowulf grabs hold of Grendel, indicating to the monster in no uncertain terms that he's not dealing with just any regular warrior.
In the ensuing melee, Grendel tries to escape from Beowulf's iron grip, but Beowulf won't let him; he's got the monster right where he wants him. While Grendel tries desperately to thrash himself free, his talons are broken, which makes him much less of a danger. Even so, he's not done yet. He comes at Beowulf, attacking him as his very life depended on it. But Beowulf gives as good as he gets, and Heorot shakes as the hero and the monster throw each other all around the mead hall.
Finally, Beowulf gains the upper hand as Grendel senses his strength draining away from him. He rips off the monster's arm, and Grendel, mortally wounded, slinks off to his den to die, never to darken Heorot's door again.