There are multiple characters in Shakespeare's Macbeth who are not present at the banquet honoring Macbeth's kingship.
First, Duncan is not present. Duncan does not attend the banquet because Macbeth has murdered him. Both of Duncan's sons, Malcolm and Donalbain, are not present given they have fled Scotland (for Ireland and England) in fear of their lives. One could also say that Duncan's attendants are not at the banquet given Macbeth has disposed of them as well.
Banquo is not present at the banquet either. Macbeth had Banquo murdered because he was fearful of his sons taking the throne (based upon the prophecies of the witches). Fleance, Banquo's son, is not at the banquet either. He, like Malcolm and Donalbain, has fled for his life.
Now, even though Banquo is dead and not physically at the banquet, he does appear in ghost form to Macbeth. (So be careful; some could consider Banquo making an appearance at the banquet.)