On the last link - I don't think Larrick was underused, I think he was misused and overused. Larrick wasn't really a villain, he was only a villain from the KGB's pov. If Stan would have played the same role - going rogue to get his own justice, nobody would have pegged him as the 'bad guy'. In the case of Larrick it was even worse, because he became a villain only because the KGB decided he was one.

So the show had a guy who wasn't exactly bad, but that we were supposed to think was evil incarnate, driving the plot. It's a problematic premise to begin with because (a) you're misleading the audience, who's meanwhile developing expectations and (b) because much of the action is driven by the wrong reaction on the KGB side.