Season four as a whole was a very cool concept (unlike season six) that bad writing and acting (mostly from Blucas and Benson, though the latter admittedly improved in later seasons) really dragged down.
I mean, hell, Adam, IMO was one of the coolest character concepts in the show's run. The problem was, he was REALLY underused and undeveloped though. He killed Walsh, then just didn't show up again until the penultimate episode (save little scenes where he really did nothing at all). Just such terrible execution, throughout the season, really.