Final answer:
Grendel is the most clearly a round character in the poem 'Grendel' as he exhibits a complex personality with various emotions and thoughts.
Step-by-step explanation:
The character in the poem Grendel that is most clearly a round character is option A, Grendel himself. A round character is one who is complex and undergoes development, often showing varied and sometimes contradictory traits.
Grendel is portrayed with depth throughout the poem, exhibiting a range of emotions and philosophical thoughts that provide the reader with insight into his character. This stands in contrast to characters such as Beowulf and Hrothgar, who may be seen as more one-dimensional or flat characters in terms of their development within the story.