Answer: A supernatural force.
Step-by-step explanation:
Beowulf is representing one epic hero that is strong, brave, intelligent, smart, and he has that excellent nature that nobody has. He is the only one and that is why the main symbol of his victory will be a supernatural force. Since he is one perfect epic hero he will always have that supernatural force or help that will help him to get through anything.
His battle with Grendel represented that he had supernatural force.