ok, with the new criteria, since you say hero, we should automatically disqualify elektra, punisher, and anyone else who murders in cold blood. taking a look at what's left, i'd say black widow or nick fury, but their age has obviously been suppressed by some serum...
that leaves me with a choice of a drunk in a tin can, a right wing nut in a bat suit,and archer, and bucky......I'll go with Jessica Jones.