2 The present offer of fair victory, 3 And soon his dreadful blade about he cast, 4 Wherewith he smote his haughty crest so high
Wherewith > With which haughty > high; proud high > high [physically]; excessively, hence: forcefully; also: loudly
5 That straight on ground made him full low to lie;
made > [Guyon made; the blow made] full > very, entirely
6 Then on his breast his victor foot he thrust; 7 With that he cried, "Mercy, do me not die,
he > [Pyrochles] die > [to death]
8 Nor deem your force by Fortune's doom unjust,
deem > estimate, judge, form an opinion of by > [by virtue of, according to] doom unjust > unjust judgement
9 That has (maugre her spite!) thus low me laid in dust!"
maugre > a curse upon (SUS) her > [Fortune's]