2 That nothing might sustain his furious force;
might > could sustain > endure; withstand
3 He cast him down to ground, and all along 4 Drew him through dirt and mire without remorse,
remorse > pity, compassion
5 And foully battered his comely corse,
corse > body
6 That Guyon much disdained so loathly sight.
That > [So that] disdained > [was moved to indignation or scorn by] loathly > loathsome [a]
7 At last he was compelled to cry perforce, 8 "Help, O Sir Guyon, help, most noble knight, 9 To rid a wretched man from hands of hellish wight!"
wight > creature