The same bravery and physical strength that make Beowulf a great warrior also make him a great epic hero, as does his willingness to die for the good of others. SparkNotes also points out that he has embodies the main features of the Germanic heroic code, including loyalty, courtesy and pride.
When Beowulf approaches Hrothgar and offers to kill Grendel, he is already a very accomplished warrior who has achieved many feats, and he is a hero to the people. His willingness to rid the kingdom of Grendel as a way of returning a favor makes him noble. The extreme danger of the task is illustrated through the fact that Hrothgar's own men's attempts to kill Grendel have been futile. Beowulf displays great courage in not only eliminating Grendel but his mother as well. Though the dangers Beowulf faces become increasingly severe, he does not turn away from them or flee. He sees them through with the constant threat of his own life. Later in life, Beowulf transforms from a young warrior to a wise king who later dies in order to save the people of his kingdom from a dragon. Before dying, however, Beowulf succeeds in killing the dragon. Although there has been debate about whether or not Beowulf is as noble at the end of the epic as he is at the beginning, he is considered a prime example of the epic hero and is given as an example in Dictionary.com's definition of "epic hero."