Boss fight
Once you’re all geared up and the steps are complete, head to the Mainframe Chamber and interact with the device in front of S.A.M.
There will be an action-filled cutscene before the fight, but it might be worth skipping on your first try. There is currently a bug with the cutscene that can cause one or more players to get stuck on a white screen. This unfortunately hindered my first boss fight attempt, as one teammate was unable to help or even watch. Some players suggest skipping the scene can help prevent the bug from even occurring.
This is definitely one of the coolest Zombies bosses in recent years, allowing you to face off against an undead T-Rex. You’ll want to aim for the critical spots on the dino, which include the eyes, the glowing patches that eventually appear on the sides and back, as well as the mouth while its puking acid.
There are four phases to the fight, and you’ll know when the phase is changing because the boss will jump onto a cliff and become immune for a short time. It’s best to save a chopper gunner for each phase, if possible. Defeat the zombie T-Rex to complete this main quest and receive a final story cutscene.