There are many cumulative achievements which are glitch, including but not limited to: Ashes to Ashes, Pigs Can Fly, Sight Seeing, Hello Nurse!, Clever Girl, Bird of Prey, et cetera. They're all DLC achievements and they were all broken when 343i released the last TU with the last DLC (Champions/Bullseye). #FixHalo4 or gimme a ~$120 refund for a broken product.