You had the fallout with the Money Train, Aceveda's sexual assault, Claudette's first brief run of the barn, the rival special crimes team. It had plenty of the type of episodes where The Shield was at its best: four different things happening simultaneously, all about to spin out of control, but never QUITE going all the rails.

About the only thing I didn't like about #3 was how they got rid of Tayvon early on. But with all the insanity involving the Money Train, I don't see how they could have kept him around.

I'd say the worst season was #4. They set up Antonie Mitchell as a monster heel in the first half, but then made him ineffective after that. By the time the made him responsible for the cop murders towards the end, it lacked any potency.

I'd have to go and rewatch the show to say whether #2 or #5 was the second best.