The achievement has not been removed, it might just be a bit tricky to get:
- Start “The Pillar of Autumn” on the Legendary difficulty (you must
be playing alone).
- After you gain control of the Master Chief, walk toward the
canisters behind you.
- Crouch jump on top of the yellow canister and then jump off.
- Move through the level as normal until you get to the bridge of the
- Trigger the cinematic by walking towards Captain Keyes.
- After the cinematic, he will hand you a pistol. Continue forward,
pick up ammo, kill the 3 grunts, and return to Keyes.
- Shoot him in the head to kill him. Doing this will make 3 invincible
troops come out of a secret room that was previously locked.
- You’ll have to lure them away from the door, by sitting in the
middle of the room, and then quickly make a dash for the newly
opened door without being killed.
- Once inside, you can look at the ceiling above and notice the “Megg”
Easter Egg using your flashlight!
Remember dear, this can take a few tries but you can use your checkpoint and still get the achievement. Also, it’s not required to kill Captain Keyes, anyone in the room works. The other NPCs don’t always die, Keyes is guaranteed for the room to open.
Let me know if it works for you.