Final answer:
Seyton is the only servant left on Macbeth's side at the end of the play. Other characters listed like Macduff, Fleance, and Donalbain have different roles and are not servants to Macbeth.
Step-by-step explanation:
The only servant left on Macbeth's side at the end of the play is Seyton. The other options provided in the question do not represent characters who are servants to Macbeth. Macduff is his enemy, Fleance is Banquo's son who escapes from Macbeth, and Donalbain is King Duncan's son who also escapes. Seyton is an assistant to Macbeth and remains with him until the end when Macbeth faces his demise. Seyton's role is not as prominent as other characters in the play, but he is there during Macbeth’s final hours, assisting him as he prepares for battle.