4 Against two foes of so exceeding might,

so > such

5 The least of which was match for any knight.

least > lesser

6 And now the other, whom he erst did daunt,

erst > not long ago; first daunt > overcome, subdue

7 Had reared himself again to cruel fight, 8 Three times more furious, and more puissant,

puissant > powerful

9 Unmindful of his wound, of his fate ignorant.

ignorant > unconscious; hence: heedless