Do you agree that Macbeth's murder of Duncan has horrible consequences for both Macbeth and for Scotland?
Yes, Macbeth's murder of Duncan has horrible consequences for both Macbeth and for Scotland. Returning from the chamber where he murdered King Duncan, Macbeth heard a voice that cried, "Sleep no more!" It is possible that Macbeth was unable to sleep thereafter and that he was suffering a mental breakdown as a result. Encouraged by the three witches to be "bloody, bold and resolute," he has become a bloody tyrant ruling by terror. Everybody has decided that he murdered Duncan. The other thanes are fleeing to England, and he is using terror tactics, killing their families and seizing their property as he did with Macduff's, to enforce their obedience.
At his meeting with Macduff in Act 4, Scene 3, Ross tells him about conditions in Scotland:
Alas, poor country,
Almost afraid to know itself. It cannot
Be called our mother, but our grave, where nothing
But who knows nothing is once seen to smile;
Where sighs and groans and shrieks that rent the air
Are made, not marked; where violent sorrow seems
A mocern ecstasy. The dead man's knell
Is there scarce asked for who, and good men's lives
Expire before the flowers in their caps,
Dying or ere they sicken.
All of this proceeds from Macbeth's murder of the good King Duncan.