In the wanderings of Odysseus in The Odyssey, which factor proves to be the most challenging to the hero’s cleverness in his attempts to return home to Ithaca?

His confrontation with the Cyclops, who has support from Poseidon, creates such formidable conflict that Odysseus must overcome brute force with deception.
In spite of his well-known sea-faring skills, it is the physical trials of navigating in treacherous seas, including weather, tides, and an unworthy vessel that tests Odysseus the most.
His encounter with Poseidon, who holds a grudge against Odysseus for blinding his son, presents the severest confrontation for the hero.
It was the hero’s trust in Calypso, whom he expected would allow him to return immediately to his wife, Penelope, that becomes the most rigorous obstacle for Odysseus to overcome.