Malcolm's Complete List of False Vices
Malcolm continues his devastating self-portrait, claiming he lacks all the "king-becoming graces": justice, truth, temperance, stability, bounty, perseverance, mercy, humility, devotion, patience, courage, and fortitude.
He paints himself as someone who would "pour the sweet milk of concord into hell" - basically destroy all peace and unity. This is the opposite of what a good king should do.
Macduff finally breaks, crying "O Scotland, Scotland!" He's realised that if Malcolm is this corrupt, Scotland has no hope - they'd just be replacing one tyrant with another.
Key Point: Macduff's despair proves his loyalty - he'd rather have no hope than accept a corrupt king.