For each Interval/Score achievement you will need to maximize your points gain. This is easier without a partner as your individual score is needed to earn this achievement. This interval has the toughest enemy pinch near the end of the Interval. You'll press a button to open a bay door and a lot of Monstrosities will spawn in to kill you. You will have to wait for the door to open enough to get in and close it while killing off whatever follows you through. On easier difficulties it's possible to make a stand and kill them as they spawn. Yet on harder difficulties it's best to run back to the previous room, close the door and wait. From there you can decide the best course of action, whether to kill them all or run for the exit. If you decide to fight be sure to have the Riot Gear from the previous room, it'll make this part much easier. Other then that there's not a lot to this Interval. You can earn 7 or so weapon challenges here (Strader, SMG, CAS, G3A3, Frag/Flash/Shock, Penetrator, Goliath, Laser, Riot).