"Man of an hard heart! Hear me, Proud, Stern, and Cruel! You ..." — Matthew Gregory Lewis quote meaning

Man of an hard heart! Hear me, Proud, Stern, and Cruel! You could have saved me; you could have restored me to happiness and virtue, but would not! You are the destroyer of my Soul; You are my Murderer, and on you fall the curse of my death and my unborn Infant’s! Insolent in your yet-unshaken virtue, you disdained the prayers of a Penitent; But God will show mercy, though you show none. And where is the merit of your boasted virtue? What temptations have you vanquished? Coward! you have fled from it, not opposed seduction. But the day of Trial will arrive! Oh! then when you yield to impetuous passions! when you feel that Man is weak, and born to err; When shuddering you look back upon your crimes, and solicit with terror the mercy of your God, Oh! in that fearful moment think upon me! Think upon your Cruelty! Think upon Agnes, and despair of pardon!