Find Johnny Gat
Head to the Broken Shillelagh to enter another simulation to find Johnny Gat. You can't use your superpowers so you'll have to rely on your good, old pistol. Fight your way from the cargo bay to the passenger areas. Keep killing the Morningstar thugs along the way until you reach the last door.
After the scene, head through the next few cabins while jumping over the openings. Keep going until you reach a nightclub. Go downstairs to find a woman being held hostage by a punk called Veteran Child. Use the stun gun to force him to let go of Shaundi(?) then switch to your other weapons and shoot him. Once he's not stunned, he will grab Shaundi again so you'll have to repeat the process again.
After killing Veteran Child, you have to fight and kill his replicated copies. Kinzie will then tell you to get a weapon from a nearby cache. Open it to get a Disintegrator. This weapon should be enough to kill the Veteran Childs permanently.
Completing this quest will have Shaundi to be part of your ship's crew. You'll also get the normal Shaundi and Fun Shaundi as your homies. In addition, the Disintegrator gun will be added to your arsenal and the West Carver Island Gateway will be opened. Several primary and side quests will be added as well.