A number of things, explained in Act 1 Scene 7.
1. Once you get started killing, it might be hard to stop. "That this blow might be the be-all and the end-all here
2. If you go around killing kings, others may get the idea and kill you. "This even-handed justice commends our poisoned chalice to our own lips."
3. It's not nice to kill your close relatives, or a king you have sworn allegiance to. "As I am his kinsman and his subject, both strong against the deed."
4. It's even worse to kill someone who is a guest under your roof. "Who should against his murderer shut the door, not bear the knife myself."
5. Duncan is a likeable old duffer; his murder will garner sympathy. "his virtues will plead like angels Trumpet-tongued against the deep damnation of his taking off."
6. Macbeth has only just been made Thane of Cawdor and would like to bask in that for a bit. "He hath honoured me of late, and I have bought golden opinions of all sorts of people which would be worn now in their newest gloss not cast aside so soon."
7. They might get caught. "If we should fail--?"
She didn't want to kill him herself, because she said Duncan looked like her dad while he slept. She did have Macbeth murder Duncan nonetheless
Yes Macbeth did hesitate to murder King Duncan, he went through allot of mental turmoil about this decision. In his soliloquy he gave good reasons for not wanting to kill Duncan 1)he is not a bad king 2) he is there in double trust. In the end Macbeth did not want to kill Duncan but it was Lady Macbeth's persuasion that caused him to commit the act. In comparison Macbeth had no hesitate in killing Banquo and Lady Macduff.
lady Macbeth prays to be unsexed because she thinks her femininity makes her weak she is too kind and gentle she needs her kindness to be taken away so she can plan the murder and make Macbeth kill king duncan
Macbeth killed Duncan because the witches predicted that he would be the king but at the time Duncan was the king so in order to be king Macbeth kills Duncan since he was the successor at the time.
The three witches told MacBeth he was going to become king. He decided this needed a little proactivity on his part. Prompted by his wife, he killed Duncan to move things along a bit faster
There is a sort of conflict in Lady Macbeth's mind between what she wants to do (i.e. kill Duncan) and what she suspects rightly Macbeth will want to do (i.e. not kill Duncan). She therefore sets about persuading him to let her plan the murder, so she can overcome the objections she knows he will make.
In Macbeth's mind there is no justification for killing Duncan. He didn't really want to do it ("We shall proceed no further in this business") and regrets it the moment it is done. In the case of Banquo, however, his reasoning has been blunted by his fear and paranoia ("My fears in Banquo stick deep."). His fear of Banquo is unfounded, but in Macbeth's mind it does provide a justification of sorts.
Physically, yes. Mentally, no. His conscious doesn't want to kill a human being - it's just ethically wrong! But his wife, sees this differently.
Because Lady Macbeth doesn't have the courage to kill the king. Therefore, she left the work to Macbeth because Macbeth was a soldier and because he the courage by killing the king because he has killed many people in wars and battles.
The daggers. He was supposed to leave them in Duncan's bedchamber to incriminate to grooms but he forgot. Lady Macbeth has to take them back, because Macbeth does not want to look at the murder scene again.
He is already guilty enough from killing Duncan and doesn't want to have more guilt by killing his friend Banquo. he think that the murderers would tell others that macbeth is the one who kill people
Lady Macbeth questions Macbeth to provoke him into taking action. She challenges his masculinity and questions his resolve in order to manipulate him into following through with their plan to kill King Duncan.