Grendel, as he is portrayed in Seamus Heaney's new bilingual edition of Beowulf evokes certain feelings of sympathy from the reader.
Grendel is described as "spurned and joyless" (line 720) and also "God-cursed" (line 711) which denotes a certain inevitability to his fate. The concept of a "family curse" is quite common throughout many myths. The fact that Grendel was a member of "Cain's clan" (line 106) shows that from the beginning of his life, he was born to be punished for the sins of his ancestor.
Furhermore, after Beowulf rips off Grendel's arm, he nails it to the wall of Heorot Hall as a trophy. When Grendel's mother comes to avenge her son, Beowulf kills her, and beheads Grendel's corpse. These events win Beowulf fame and fortune, and he returns to his native land a hero. Beowulf himself describes his childhood, and says that everyone thought that he was just a clumsy, awkward weakling. The killing of Grendel and his mother won respect and fame for Beowulf. In a sense, it seems that they were only born so that they could die by his hand.