In what ways does Harrison represent both supremely heroic qualities and potentially destructive qualities?
Harrison Bergeron represents the supremely heroic most immediately in his gifts. He is handsome beyond what society can accept, physically gifted (strong, graceful, etc.), and strikingingly intelligent. Along with those gifts come his internal qualities: he takes a stand at the story's end, and makes a huge heroic gesture. He chooses glory over long life.
That leads to his destructive qualities: he chooses glory over long life. He makes a choice that contradicts the laws of the community, and is killed for it.