What traits make Beowulf different than the negative characters in the epic?
Beowulf is different from the negative characters in the epic in his lack of greed. He does want honor and glory, but he does not want payment. The reason he is willing to take on the task of slaying Grendel, and later, Grendel's mother is a matter of honor for him. He may be accused of being egotistical, but his deeds certainly back up his confidence.
He is also concerned for his fellow men, especially his own warriors. He takes on his tasks in an archetypal heroic way: alone. He fights and kills the "villains" in the story. He does not leave the dirty work to his men.
He further demonstrates his lack of greed when he kills the dragon, not for treasure, but to save his people. His heir, Wiglaf, then assumes Beowulf's mantle and continues his tradition of selflessness by burying the treasure instead of using it.
Beowulf is the typical Epic Hero. He is brave and leads his men. However, he does not endanger his men if it is a task that he can do himself. He gains their loyalty which is evident when he is losing his own life at the end of the poem. His brave man slews the dragon and Beowulf dies.
Beowulf was the strongest man over other men. He was also noble and loyal. He does not keep secrets from others nor his men. He lets them know what battle and why they will undertake it. He takes on challenges to help other kings in need of a brave warrior and unlike some kings, he never lays down his sword but remains beside his men in battle until the end of his life.