"The Once and Future Slab" is the Chapter 12 story mission in Borderlands 2. You get it after completing the mission Wildlife Preservation.
Take Roland's Note
Go to Thousand Cuts
Destroy Mortar Beacons 0/3
With the Slab bandit clan on your side, destroying the Hyperion bunker that defends Control Core Angel should be relatively easy. Emphasis on "should."
Blue Shield or Rocket Launcher, Money and XP
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The Man Who Would Be Jack