Anvilicious: In season 2, the writers really, really want the audience to know that human trafficking is bad.
Critical Research Failure: The second episode has many, many glaring inaccuracies regarding 5.7mm handguns and, for that matter, firearms in general. Many plot points of the episode rest on facts that anyone with even basic knowledge of firearms would find gratingly incorrect.
Another, more minor but just as aggravating one: Charlie claims her Italian tomato sauce is a thousand-year-old recipe, but tomatoes are a new-world crop and have only been used in Italian cooking for a few centuries at best.
Possibly an in-character error, as she tells the story of the recipe differently each time, which is specifically pointed out by other characters.
Darkness-Induced Audience Apathy: Between Mike and Paige's increasingly idiotic fight over Sulla and his trafficking operation, Jakes' relationship problems, and Briggs'... Briggs-ness, plus a number of utterly unpleasant villains, season 2 left viewers with very few characters to root for. Thankfully, the third season was much more lighthearted.
In the first season, Paul Briggs kills Juan Badillo and tricks several of his housemates into helping him cover it up.
In the second season, Mike Warren chooses to protect Sulla and his human trafficking operation because it's the only connection to the Solano Cartel left in California. His actions directly result in one of the girls being murdered. He then helps cover up the murder to prevent Paige from shutting the operation down.
Paige crosses it when she betrays Mike and has him killed.
Spoiled by the Format: Really more a case of Spoiled By The Marketing. Since so much of the material (such as the poster on the main page) focus on the "core six" of Mike, Briggs, Charlie, Johnny, Paige, and Jakes, it made it pretty clear that Lauren and Donnie weren't gonna be around for very long.
What an Idiot!: Paige firmly grabbed the Idiot Ball in Season 2 in relation to the sex slavery ring. While it is undoubtedly a horrible circumstance, she became too emotionally wrapped up in the case and her only concern became saving Lena and wouldn't listen to any reason outside of her own. She ignores the fact that more women would just come in a few weeks to replace the few they could immediately save, which would be at the expense of losing track of the entire operation and everything going on they're trying to stop. Her obsession leads her to reveal Mike's location to Markham, then reveal what she had done to Briggs, who fails to stop Markham from killing Mike.