Duncan. This is not a good quality in a king. His inability to judge others continuously amazes him: "There's no art to find the mind's construction in the face. He was a gentleman on whom I built an absolute trust."
Banquo warns Macbeth that the witches may use truths to lead them to their ultimate downfall, by upsetting the natural order and manipulating their desires. He advises Macbeth to be wary of the witches' prophecies and not to let them cloud his judgment or drive him to commit evil actions.
When Duncan arrives at Inverness, Macbeth's castle, his mood is trusting and unsuspecting. He sees the castle as a place of hospitality and safety, not foreseeing the betrayal that awaits him.
After MacBeth receives the predictions from the witches he writes a letter to Lady MacBeth detailing the whole situation. He calls her his "dearest partner of greatness" and is very trusting of her. He is also subject to much influence from her since she is the one who later convinces MacBeth to kill the king, Duncan, when he is resolute on not doing anything of the sort.
Many many actors have played the part of Macbeth in many many productions over the last 400 years. There are far too many to list or even to find out about. David Garrick was famous for playing Macbeth. That was in the 1700s.
Hola
The milk of human kindness.
Duncan calls Macbeth "O worthiest cousin!" and "Noble Macbeth" as signs of his trust and admiration for him. Duncan also says, "There's no art to find the mind's construction in the face," indicating his belief that one's true intentions are not always apparent from outward appearances.
The major synonyms for trusting are two that suggest the person is "too trusting" -- credulous and gullible. There does not seem to be another good term for someone who has justifiable faith in others.
The difference is that Lady Macbeth at first wanted Macbeth to kill Banquo and Macbeth was too scared to do it. Later on in the tragedy, Lady Macbeth gets haunted and gets mentally ill and Macbeth keeps on killing people.
The theme of manliness, which Lady Macbeth used in Act 1 Scene 7 to persuade Macbeth to do the murder, reappears in this scene. Lady Macbeth hopes to make Macbeth behave according to her wishes by questioning his manhood as she did before: "Are you a man?", "these flaws and starts . . . would well become a woman's story . . .", "Quite unmann'd in folly?". Macbeth buys into it: "protest me the baby of a girl", "I am a man again." But what Macbeth is dealing with is far too powerful to be controlled by this kind of talk.
Macbeth might advise Othello to be wary of ambition and its consequences, drawing from his own experience of the destructive nature of unchecked ambition. Othello could caution Macbeth about the dangers of jealousy and trusting the wrong people, given how his own jealousy led to tragic outcomes.
One answer: Duncan is insightful, respectful and shows moral order for the little time he has in the play. Another: Duncan is far from insightful: he is astonished by the treason of Cawdor ("He was a gentleman in whom I placed an absolute trust."), chooses the feckless Malcolm as his heir instead of the better-qualified Macbeth, and is oblivious to the resentment Macbeth feels over being passed over. He is a good man but not a very good king.