Defining "hero"

Merriam-Webster: "Etymology: Latin heros, from Greek heros
1 a : a mythological or legendary figure often of divine descent endowed with great strength or ability b : an illustrious warrior c : a man admired for his achievements and noble qualities d : one that shows great courage
2 a : the principal male character in a literary or dramatic work b : the central figure in an event, period, or movement
3 plural usually heros : SUBMARINE 2
4 : an object of extreme admiration and devotion : IDOL

Oxford English Dictionary: 1. Antiq. A name given (as in Homer) to men of superhuman strength, courage, or ability, favoured by the gods; at a later time regarded as intermediate between gods and men, and immortal.
The later notion included men of renown supposed to be deified on account of great and noble deeds, for which they were also venerated generally or locally; also demigods, said to be the offspring of a god or goddess and a human being; the two classes being to a great extent coincident.

2. A man distinguished by extraordinary valour and martial achievements; one who does brave or noble deeds; an illustrious warrior.

3. A man who exhibits extraordinary bravery, firmness, fortitude, or greatness of soul, in any course of action, or in connexion with any pursuit, work, or enterprise; a man admired and venerated for his achievements and noble qualities.

4. The man who forms the subject of an epic; the chief male personage in a poem, play, or story; he in whom the interest of the story or plot is centred.