The following is a walkthrough for Pier 69 in GTA San Andreas.
Now that you have killed Jizzy B., you have to take out the other two heads of the Loco Syndicate, Mike Toreno and T-Bone Mendez. In addition, T-Bone and Toreno will be attending a meeting with the Ballas in Pier 69 and your former Grove Street Families homie-turned-enemy Ryder will be there, so you can take revenge on him too.
When CJ arrives at Pier 69, Cesar Vialpando will be waiting on the roof of a building across the pier. When arriving, Cesar will hand CJ a sniper rifle. Shoot down all of Mendez's guards to allow the Mountain Cloud Boys to take their place. Eventually, T-Bone Mendez and Ryder will arrive with their escorts to the deal, but, in an unexpected turn, Mike Toreno arrives in his black Maverick helicopter and sees the guards' bodies on the roofs, so he flees. Toreno's flight alerts Mendez and Ryder and a huge gun battle erupts between the Ballas, the San Fierro Rifa and the Mountain Cloud Boys.
You will then enter and fight Mendez's goons while defending both Cesar and the Mountain Cloud Boys. Eventually, all the Ballas and Rifa men will be dead. After you kill the Ballas and Rifa, you then have to kill T-Bone Mendez. When shooting him enough a cutscene will appear showing both CJ and Cesar shoot T-Bone, who's corpse then falls into the water.
Ryder then tries to make a getaway, he jumps off the Pier and starts swimming towards a Speeder boat, you must kill him by either swimming towards the boats and giving chase doing a drive-by or use a gun and kill him from the pier, either way works. The mission is passed but Toreno is still on the run.