What about saving a country, changing the route of history, shaping humanity's conscience - eating a crocodile...? No. Perhaps a hero of one's own life and nothing more. We have here two possibilities, I think: to see David Copperfield as a work of mediocrity, or as a work where a personal life substitutes the whole of humanity, a world by itself, worthy enough to have its own hero. Remember the subtitle: "The Personal History And Experience Of David Copperfield The Younger". Romanticism is here, with all its mediocrity and all its genius.
To find out who the hero is, in that context, we must ask David himself, because this hero is the hero of his life. We can not stare at the persons of the novel and establish criteria of heroism; we must have David's answer to this question. This answer, in my opinion, is given at the end of the story, where his hero stands "pointing upward", above all melting realities and illusions, when a life concludes and the soul becomes the face of the one that she loved.