What suspicion about Macbeth does banquo reveal in his Soliloquy

He reveals that he thinks Macbeth has killed Duncan to achieve his newly found success,

Thou hast it now: king, Cawdor, Glamis, all,. As the weird women promised, and I fear. Thou played'st most foully for 't.

Banquo suspects bcuz of all the things that the witches predicted have happen and he finds it more than a coincidence tht the events coincide with the murder of duncan.