No Pain, No Gain

From Halopedia, the Halo wiki

No Pain, No Gain is an achievement in Halo: The Master Chief Collection. It is unlocked by completing one mission with the LASO skulls enabled. The achievement is worth 10 Gamerscore.

This achievement cannot be unlocked by playing any cinematic-only mission, such as Arrival in Halo 3, or Prologue in Halo 4. It also cannot be unlocked in Spartan Ops, likely because Spartan Ops does not feature the Iron skull.