Wesley Owen Welch
Wesley Owen Welch was the personal assistant to Wilson Fisk, both in his official capacity as president of FiskCorp and as the Kingpin. When Fisk sought to frame Nikolas Natchios as the 'real' Kingpin, he had Wesley create a paper trail. Wesley was also the one who hired Bullseye to eliminate Natchios later on.
In the Director's Cut of Daredevil, Wesley plays a much more important role than merely the Kingpin's henchman. His name, or rather his initials, 'W.O.W.', are what led Franklin Nelson and Ben Urich to the true identity of the Kingpin after he presumably killed Lisa Tazio to frame Duante Jackson.