Odysseus loses his shipmates after they leave the island of Thrinacia. Thrinacia was home to cattle of Helios, the Sun God; Circe had warned Odysseus to ignore the island of Thrinacia and the cattle belonging to Helios. Odysseus pleads with his men to leave the cattle alone, for he knows of Circe’s warning. Odysseus and his men are waylaid by a sea storm, no doubt the fault of Poseidon, and his men end up eating some of the cattle. Since Odysseus played no part in the eating of the sacred cattle, Zeus avenges Helios's rage by killing all of his men, sparing only Odysseus.
Throughout the entire journey, Odysseus' men die off in adventure after adventure, leaving Odysseus as the sole survivor in the end. In chronological order of Odysseus' journey (not of the epic's narrative structure), here are the ways in which the shipmates die/are left:
Lotus-eaters: No one dies, but Odysseus drags them all back to the ship and sails off.
Island of the Cyclopses: The Cyclops Polyphemus captures the men in his cave. He eats two of them at a time for a few days. (KEY MOMENT: Polyphemus' father is the god of the sea, Poseidon, who curses Odysseus to lose all of his men!)
Aeolus, master of the winds: No one dies, but Odysseus' men accidentally cause them to be blown off course.
Laestrygonians: Cannabalistic giants who destroy all of Odysseus' ships except one, the one he is on.
Circe: A sea-witch who turns half of the remaining men into pigs.
Underworld: Only Odysseus goes, no deaths.
Sirens: No one dies.
Scylla: Sea monster who kills six of the men.
Helios: Sun-God. Odysseus' men disobey orders and eat Helios' cattle. Helios demands vengeance/justice from Zeus.
Charybdis: The other side of Scylla, a whirlpool monster who destroys the ship. All of the men drown except Odysseus in order to satisfy Helios.
Calypso's island: At last, Odysseus is alone...