He hates Odysseus because Odysseus hurt Polyphemous the Cyclops, Poseidon's son or at least one of his creations. Poseidon also supported the Trojans in the Trojan war Odysseus helped the Greek forces defeat the Trojans.Poseidon does a number of things to slow Odysseus down. He constantly gives them storms at sea. He also has a monster "Scylla" who kills six of his men. He punishes anybody that tries to help Odysseus by turning them into stone.
But now Lord Poseidon, the Earth-Shaker, returning from visiting Ethiopia, saw him far off from the Solymi range, as he came in sight over the water: and the god, angered in spirit, shook his head, and said to himself: ‘Well now, while I was among the Ethiopians, the gods have certainly changed their minds about Odysseus! Here he is, close to Phaeacian country, where he’s fated to escape his trials and tribulations. But I’ll give him his fill of trouble yet.’ (Book 5)