Why is Poseidon forever against Odysseus?

Poseidon is against Odysseus primarily because Odysseus blinds his son, the Cyclops Polyphemus, during his escape from the island of Aiaia. Angered by this disrespect towards his son, Poseidon vows to make Odysseus's journey home as difficult as possible. Additionally, Poseidon represents the unpredictable nature of the sea, and Odysseus's cleverness and defiance challenge the authority of the gods, further inciting Poseidon's wrath.