After the war Harry finds the Hallows won't leave him, and call on him to become a hero. Not just to the magical world but to the regular and international ones as well. Harry, getting tired of a bland and uninteresting life, gives up on being normal and takes up the armor and image of the Spirit of the Black Knight.
Rules:
Harry actually wears old knight armor(heavily enchanted of course)
Harry owns an international company that gives him access to the things he needs as a hero(ex: weapons company, medicinal company, tech company, all of the above, etc...)
Old potter manor/castle filled with special family magics
Not god like, but easily stronger then average criminals Business man Harry
Not a romance centered story
Suggestions
Maybe having drifted from his friends after Hogwarts
Rune mage
Ancient Magic
Special Hallow powers(ex: resurrection stone has ability to summon wraith hounds, cloak to summon a concealing and dark mist, etc...) to more fit the image
joins justice league
Takes up London as main city(like Batman and Gotham, or Superman and Metropolis)
Hedwig Survives!
Animagus of a Dragon(again to go with the image)
please no slash(nothing against it, but I don't want to read it)
Rivalry with Batman, because of similar but differing methods
maybe picks up a young orphan as a 'squire'(sidekick)
And who can forget the Steed? And what fits a black night better than a Thestral(or Night Mare)?