Open Season

Open Season is a side quest in the Fallout 4 add-on Nuka-World.

Detailed walkthrough
The quest can be started at any time after exiting the gauntlet in Taken for a Ride by either speaking with Mackenzie Bridgeman in the Nuka-Town market or openly murdering any named or unnamed gang member. The quest may also be given by Preston Garvey.

The Sole Survivor must go to the gang leaders' locations and execute them: Nisha will be in Fizztop Mountain, Mags and William Black will be in the Parlor and Mason will be in Bradberton Amphitheater. The player character can execute them in any order, but once one of the leaders is killed, all the raiders in the park will become hostile to the player character, including Shank. This will involve a lengthy battle to clear Nuka-Town USA of all gang members, which involves killing eighty or more named and unnamed gang members in total. In addition to each gang's base of operation, the player character will also need to clear out Cappy's Cafe and Nuka-Town market of any raiders there. The optional objective to restore power to Nuka-World power plant may be done at any time. After all the leaders are dead, speak with Mackenzie Bridgeman again to complete the quest.

Bugs

 * If completed before starting any quests given by Porter Gage, he will stand idle on top in the overboss's room, and will not provide any dialogue unless he is engaged in combat.
 * After completing the quest, leaving Nuka-World, and then coming back, all of the traders will unequip all of their inventory items, including any clothing, instead of only their explosive collar. It is still possible to trade with them.
 * This can be fixed by using the console command and re-equipping their clothing through the trade menu.
 * If one completes this quest after building any raider settlements, they may be unable to clear the raider settlements if the settlements contain turrets. The turrets will be indestructible, staying alive at 1 HP, but attempting to use the workshop will give a message instructing the player character to first clear the area of all enemies, even though all raiders are killed. Reducing the health of all turrets to minimum and then leaving the area and later returning will reset the turrets, making them friendly again.
 * When entering the market and killing the raiders there so that the Sole Survivor can talk to Mackenzie, she and most of the other NPCs will continue to cower even after all the enemies are gone.
 * To engage Mackenzie in dialog, use the console to disable and re-enable her.
 * Reload a previous save prior to killing the raiders in the market.