Grendel ran away because Beowulf ripped his arm off. Grendel was used to coming out of battles uninjured because he was impervious to weapons.
Grendel gets his arm torn off by Beowulf .
Beowulf holds onto Grendel's arm so when he starts to flee his arm is ripped off and he eventually bleeds to death
Beowulf cut grendel's arm off and saved it as a trophey
Beowulf tears Grendel arm off and Grendel dies. Beowulf hangs the arm up on a wall but it disappears in the morning.
Grendel get fatally wounded and then dies.
Beowulf's men tried to help him by striking Grendel with their swords, but Grendel could not be harmed by any blade on Earth.
Beowulf kills Grendel, Grendel's mother, and a fire-breathing dragon.
In the story of 'Beowulf the Warrior' Grendel is the very first monster that Beowulf encounters. After slaying Grendel, he destroys Grendel's mother and a dragon.
Beowulf and his men fall asleep in Heorot, Grendel comes into the hall and attacks them. Grendel devours one of Beowulf's men, Beowulf had been feigning sleep and jumps up and grabs Grendel's arm. The two have a long violent battle that nearly brings the hall down. Finally Beowulf tears Grendel's arm from his body at the shoulder. Grendel runs to the marshes to die.
Beowulf does not fight Grendel's mother until after he has defeated Grendel.
They fight each other. Beowulf kills Grendel.
Beowulf overcomes Grendel by engaging in hand-to-hand combat with him in the mead hall Heorot. Beowulf tears off Grendel's arm, causing the monster to flee back to his underwater lair where he ultimately dies from his wound.