Grendel for one, is totally wild and is therefore shown as evil. His wild home, “Grendel, who haunted the moors, the wild marshes, and made his home in a hell not hell but earth.” shows his wild, untamed, and therefor evil nature.
Grendel’s wilderness is countered in mankind’s ways, especially Beowulf’s.
Beowulf is tame and civilized, the epitomy of goodness and purity. Beowulf doesn’t fight evil in a wild manner, rather, as shown in his first battle with Grendel. First off, Beowulf is pure and shows this before his battle when he removes his armor and vows not to use a weapon to defeat Grendel.
Defeating Grendel, he shows that man, without armor and weapons, can defeat evil in any form including that of his foe Grendel. This deed serves throughout the epic serves as a symbol of Beowulf’s Goodness.