By the end of Season 2, Vic has stopped protecting Kern and his interests, causing a rift between the two.
In Season 4, the One-Niners were the target of coordinated efforts by Captain Monica Rawling to bring them down using asset seizures and court injunctions, using an Anti-Gang Task Force coordinated by Vic. This was done mostly in response to the release of gang leader, Antwon Mitchell. Vic eventually began to bring down the organization, but could not completely dismantle it due to controversies within the department involving his own past and Rawlings' seizure program.
When Lem took a plea deal and was sent to prison, Vic made a deal with Antwon to secure Lem's safety in return for robbing a police warehouse. During the robbery, Kern was killed by Antwon's hand-picked successor, Moses. Despite the Strike Teams' co-operation, the deal went bad, and Antwon told Vic that Lem would die once he arrived in prison.
In Season 6, a group of One-Niners try to leave the gang for a non-criminal life, only for Moses to brutally kill almost everyone who tried to quit. He also warns Vic that, if left out of option, he will reveal Vic's role in the warehouse robbery.
In season 7, the One-Niners are revealed to be the 5th most powerful gang in L.A. This annoys Moses since the resulting police attention hurts his drug trade. In return for reduced police scrutiny, he agrees to protect Ellis Rezian who has been marked for death by the Mexicans.
- Antwon Mitchell - Head of the One-Niners in Season Four.
- Dead-Eye - Henchman of Antwon's seen in his house.
- Weed - Temporarily replaces Antwon as head of the One-Niners when Antwon is thrown in jail.
- Donzell "Urkel" Prince - Gun dealer for the One-Niners.
- Frederick "Freebo" Bokamp - Street soldier for Antwon and the One-Niners.
- Halpern White - Second in command of the One-Niners gang under Antwon Mitchell in Season Four.
- Kern Little - Head of the One-Niners in Season Five.
- Slap - Temporary bodyguard for Kern Little.
- Moses - Head of the One-Niners in Season Six.
- Rondell Robinson - Drug dealer with ties to the One-Niners and friends with Kern Little in Season One.
- Aaron - One of Rondell's dealers.
- Mo - Member of the One-Niners shown in Season Two.
- T.O. Osmond - Partner-in-crime and later rival of Rondell; later replaces Rondell thanks to help from Vic Mackey.
- Big Forty - One of T.O. Osmond's workers.
- Like the notorious real-life Blood and Crip gangs, the One-Niners identify themselves strongly with one color (in this case purple), wearing it on various items of clothing.
- The One-Niners have also appeared in other shows like Sons of Anarchy, which was created by The Shield co-writer Kurt Sutter..