Who is the protagonist and hero of this story and what great feat did he do?

The protagonist of the Odyssey was Odysseus, a hero who fought alongside the Greeks at Troy. Blessed with great physical strength (which he amply demonstrates, despite his years, at several moments), he has an equally keen mind that bails him out of many dire straits. There is no better "improviser" or "strategist" in Greek mythology, though the label attached is often "cunning" or "deceiver"; indeed, many Greeks saw Odysseus' habit of lying as a vice and a weakness. His penchant for disguise complements his ability to make up plausible stories about his background. Although Odysseus' ingenuity comes across as his chief weapon, his Achilles' heel of sorts is the frequency with which he falls victim to temptation and makes grave tactical errors, none more so than when adding insult to injury to Polyphemus and revealing his true name. Still, Odysseus is aware of this flaw, and bids his men to tie him up when they pass by the Sirens, the exemplars of temptation. By the end of his journey, he has learned to resist temptation, willingly suffering abuse by the suitors to meet his eventual goal of destroying them.

Despite his occasional gaffe, Odysseus is a courageous and just leader who inspires admiration and respect from his shipmates and servants; the faithfulness of his dog and swineherd after so many years says as much. The near-constant protection he enjoys from the goddess Athena seems justifiable for a man who has endured so many hardships, and cast away so many luxuries, to reunite with his beloved family.