A eulogy is written after someone dies, commemorating and celebrating the person’s death. Banquo’s eulogy would focus on how he was a brave soldier, loyal to the king, and loyal to Macbeth.
Macbeth and Banquo were both praised for their efforts in the battle where Macbeth killed Macdonwald.
As sparrows eagles, or the hare the lion.
If I say sooth, I must report they were(40)
As cannons overcharged with double cracks,
Doubly redoubled strokes upon the foe. (Act I, Scene 1)
Clearly, Banquo’s eulogy would include some mentions of this battle. You would want to mention how he was brave, fought well, and came out alive. He stayed by Macbeth’s side.
Since Banquo and Macbeth were clearly good friends, and Banquo had Macbeth’s interests at heart, his support of Macbeth as a captain and a king should be mentioned.
Banquo was a family man. His son Fleance got away. If Fleance talked, he would tell everyone how his father supported him.
O, treachery! Fly, good Fleance, fly, fly, fly!
Thou mayst revenge. O slave! (Act III, Scene 3)
Remember that a eulogy is going to be celebratory but somber. It is a celebration of someone’s life and a mourning of their death.