Question

What does Banquo suspect of Macbeth when he says that (Macbeth) play'd most foully
fort"

Answer 1

In Act III, scene 1, Banquo says "Thou has it now: king, Cawdor, Glamis, all, as the weird women promised, and I fear thou play'dst most foully for 't." Banquo suspects that Macbeth had a hand in it. ... He wants to remain loyal to Macbeth (as the king) but he does not trust him at all.