To be destroyed, to be slain - She here repeats the words which Haman put into the decree. See Esther 3:13.
Could not countervail the king's damage - Even the ten thousand talents of silver could not be considered as a compensation to the state for the loss of a whole nation of people throughout all their generations.
The king now learned, perhaps for the first time, that his favorite was a Jewess.
Although the enemy - i. e. “although the enemy (Haman) would not (even in that case) compensate (by his payment to the treasury) for the king‘s loss of so many subjects.”