Act 2: Nightfall - 3. Trolls Under the Bridge
Get ready for one of the toughest fights in the game. As soon as the Corpser goes under your feet, go for the slab of concrete to the right of the car. Hopefully the Boomer will come for you, so be patient and ready your Frags. When he is in distance just toss all you got at him. Make sure you are to the side near the wall, and then pop up to take out Drones. When the area around the tree is clear, move up the slab and then look for the two windows in the building on the far end of the yard. Take out the two snipers, then just have at it with the remainders; a few guys will appear after the fight is over, so be ready.
Three ammo crates in the area and some Frags in an opened doorway near the truck. Grab the Boomshot if you wish. Head through the opened doors to the giant room with catwalks. Some Wretches attack up near the exit, so let your team run ahead of you. When you come outside four more beasts will approach, two up high and two on the ground. Go down the steps, turn around, and then go pick up COG #14.
Some ammo in the rubble in the corner. Snake through the path and ready for two Drones and one Boomer after the Corpser goes away. Some ammo tucked away in the corner.
Go forward with a Frag in hand. As soon as you mantle over the slab go to the right side of the car. Screw pushing it, just Roadie Run to the van at the other end of the bridge (not the first car). Just stay in cover behind the van and look up at the Troika, then blindlob a Frag to the gunner (don't aim too closely to the van or you will miss and be sure to aim high). Whip out the Lancer and open fire. A lot of Wretches and Drones pour out of the hole down the road. The hole is too far away, so just kill them all.
*Oh yeah, free Frags by the van too.
Continue onwards until you reach the gate. Go to the the spot behind the blue mailboxes for COG # 15. Approach gate.