Skulltaker Halo 2: That's Just... Wrong
From Halopedia, the Halo wiki
Skulltaker Halo 2: That's Just... Wrong is an achievement in Halo: The Master Chief Collection. It is awarded for collecting the That's Just... Wrong skull in Halo 2: Anniversary on The Armory while playing on Legendary difficulty. The achievement is worth 5 Gamerscore, and the Xbox art is a still from the Halo 2: Anniversary cutscene The Heretic showing the Swords of Sanghelios Sangheili that converses with Jameson Locke.
At the beginning of the level, after you power your shields for the first time, Sergeant Johnson shows up on an elevator. Wait in the room until Johnson starts berating you, telling you to get into the elevator. You MUST wait for him to say "Would it help if I said please?" (this takes approximately four minutes and forty seconds). Once he says this, get in the elevator, and go up to the tram. Get on the tram, and face towards the INSIDE of the building. Press up against the glass doors towards the inside of the building. You should hold down the "action/reload" button (default "X"), and you will pick up the Skull. It's on a stack of crates, near the end of the tram ride.