Grendel

Grendel is one of the three antagonists in the Anglo-Saxon epic poem "Beowulf" (AD 700–1000). 
Grendel is usually taken to be some kind of monster, though this is the subject of scholarly debate. 
In the poem, Grendel is feared by all but Beowulf, who kills him and his mother at the end of the poem. He is the descendant of the biblical murderer Cain.