Have to finish on different settings
Using the Scarab Gun method, fly to the building that is cut in half. It is on one of the floors. Can shoot it about
2 Choices here
You have to do these on legendary mode
After you awaken, go straight ahead. There should be a passage in front of you and walls around you. Notice the ledges on the walls. Jump up them, then onto the roof. Go to the right (Not towards the skull) and go across that wall. Grenade jump to the top of that roof, go across to other side and get up that roof.
Then, follow the path.
Side note: If you see a hole on one of the roofs, fall into it to get a sword
Enter as profile name
In Metropolis, fight up until tunnel. Then, destroy all vehicles EXCEPT FOR ONE BANSHEE. Then, slowly get in your vehicle and slowly back down the tunnel, making sure the banshee is following. It is hard, but at the end, before you go up to the outside, just before loading bit, get in. You should get in as it loads and you should keep in. Then, go fly up to the highest Bridge to get the Scarab Gun. It looks like a Plasma Pistol. DO NOT AIM AT FEET
Get a banshee in last level. Fly to the right of the building when the door is busted. Go towards bottom right and you should get the cutscene with Tartarus. You can then fight him.