Trys to justify himself
Lady Macbeth wants to use their daggers to stab Duncan and then smear them with Duncan's blood. When Macbeth fails to do this, she does it herself.
In Macbeth," the murders of Banquo and Duncan reflect the changes in Macbeth's status. While he had to be pushed by his wife to kill Duncan himself, in the case of Banquo, he hires murderers to do the job since he is now in a position where he wants to be as far away from dirty deeds as he can get.
Macbeth is the first person to see King Duncan dead after he murders him in his sleep. Lady Macbeth later discovers the body as well.
As Macduff was going to wake King Duncan he discovered that King Duncan had been killed.
A major character trait of Macbeth and Lady Macbeth is that (to a certain extent) they regret the murders of Duncan, Banquo, etc. It eventually drives them into madness
Macbeth brings back King Duncan's bloody daggers to the castle after he murders him.
Duncan is his cousin. Duncan is his king. Duncan is his guest. If he murders Duncan, he invites others to murder him. Many people like Duncan for being a nice guy and will be angry when he is killed.
One example of violence in Macbeth is Macbeth's murder of King Duncan in Act 2, Scene 2. Macbeth's ambitious desire to become king drives him to commit this heinous act, illustrating the destructive consequences of unchecked ambition and the violence that can arise from it.
At the end of Shakespeare's play Macbeth; Malcolm, son of Duncan is proclaimed to be King of Scots. (In actual history, Macbeth was succeeded by his son Lulach; who was then was assassinated and deposed by Malcolm)
The crowning ceremony in Macbeth takes place at Scone, where Macbeth is officially crowned as King of Scotland. This event is significant as it marks Macbeth's ascension to power after he murders King Duncan.
Macbeth wishes the knocking at the gate could wake Duncan from his sleep after he murders him, so he could continue to act innocent.