Skulltaker Halo 2: Catch
From Halopedia, the Halo wiki
Skulltaker Halo 2: Catch is an achievement in Halo: The Master Chief Collection. It is awarded for collecting the Catch skull in Halo 2: Anniversary on Metropolis while playing on Legendary difficulty. The achievement is worth 5 Gamerscore, and the Xbox achievement art is a still from the Halo 2: Anniversary ending cutscene for Cairo Station, depicting John-117 riding a Chershi-pattern void maker while the UNSC Feeling Lucky is hit by an energy projector from the Day of Jubilation.
Right after you exit from the underground highway, you'll come to a large open-air circular area with a handful of Jackal Snipers and some Elites. The quickest way to get safely to the Skull is to get the next checkpoint by jumping into the Warthog and letting the Marine drive you to the next area. Jump out of the Warthog and backtrack to the large room, and clear the area. Or you can get your Warthog from the bridge and just run right through the platforms and the other part until you reach the place where you find the Wraiths attacking the building where the Marines are (but you don't have to fight them) and then go back and the enemies will be gone when you go back. You will see a large semi-circular beam going from one of the main platforms that goes from the ground up to the top of the two towers. Do a Grenade Jump at the bottom of this beam and walk all the way to the top. Jump over to the ledge of the left tower. Walk to the end of the ledge and you will find the Catch Skull. The Sputnik Skull may be helpful if you have trouble Grenade Jumping.