Answer and Explanation:
Grendel is a formidable opponent, because he is basically invincible. Grendel is large, violent, strong, powerful, with little rationality and indestructible and immune to weapons attack. This makes him a very difficult opponent to be defeated, allowing whoever manages to stop him to be a man of great power and honor. People who try to help Beowulf are completely shattered by Grendel and the weapons are useless because Grendel's skin is not harmed by them, but the weapons are completely harmed by Grendel. Grendel represents complete evil and his defeat is very significant, because it shows that no matter how invincible evil is, good always wins.
