Although not technically a villain, Thomas Bolt does at least appear as one. Hes the mayor of Star City, who becomes Steelclaw to infiltrate the citys drug cartel and ultimately reduce crime, although naturally this draws the attention of Green Arrow. Such a character would fit on the show, which obviously already involves not only vigilantism but also an established drug-scene, and he could be a straight-up villain if necessary. Oh, and Starling City could always do with a new mayor.