Best: Agent Van Alden
Most would put him on their worst list, and, yeah, his whole illegitmate baby, warden-like relationship/business agreement with Lucy (Paz de la Huerta) rarely affected the main plot, but dude is so odd and creepy that it was always compelling, in large part to Michael Shannon's great performance. Plus, there was that hilarious attempted arrest scene, which also played up one of this series' larger themes: Sometimes, attempts at redemption aren't enough to erase one's sins. Everyone pays.
We'd be questioning Shannon's continued contribution to the series, but the mob history afficionados have already pointed out that his new home is conveniently in Cicero, which, historians, if Boardwalk sticks to the real-life past, will eventually become a significant crime hub for Al Capone (Stephen Graham).