Jamm is the only character that made me want to turn off Parks & Rec. The show doesn't work tonally with villains. They need to just be other good people with different goals (Jan Barkley/Bobby Newport, Dave in his return episode, etc.) Craig, I liked Craig! Why does everyone complain about Craig?
Anyway very much enjoyed the final season, not the greatest but hey, it went out on a strong note, and that made me happy.
I also hated Jamm, but I barely tolerated him because he was a caricature used to punch home the jabs made at politicians. He even narrates the whole process with recalling Knope, and that, I think, is what made Jamm a failure. He was used by the writers to slap the audience with the point. Many of the jokes in the show worked because they were satire that we could just enjoy. Jamm was the equivalent of explaining the punchline three or four times to someone who doesn't need an explanation.
Craig was just a weak attempt at throwing in quirky comedy, but it just made his character so awkward. The passive-aggressive April and the seething anti-government Ron were done so much better (though Ron's shtick started becoming as subtle as a brick as the seasons progressed). Craig's behavior seemed to be more like "Hey, you like funny, right? This is funny. THIS IS FUNNY!!!!" But Craig was still a far better character than Sheldon from BBT.
Andy's character barely managed to avoid the same fate by having some depth. His naiveté could only be tolerated for so long, but I was able to accept him because he did become more than a one-trick pony. They kind of tried to give Craig some depth with his romance, but it was too little too late.