Alien Breed 3: Descent Trophies
Survivors
Achieve a time of 8 minutes or better on any multiplayer survivor map.
Similar to Survivor, this time you must survive for 8 minutes with a partner instead. This can be done locally or through PSN. The same strategies still apply, only this time since you have a partner now, you two must coordinate and split the items in the stage evenly, or else one of you will eventually run out of ammo and have a much harder time surviving.

Also, try to survive as long as possible, as you'll be going for 250 kills at the same time as well. The 250 required kill count is shared among you and your partner. If you killed 140 aliens and your partner killed 110, the trophy will unlock for both of you.

Again, I recommend playing on the Onslaught Map, using nothing but the assault rifle. The same strategies still apply as with Survivor, only this time make sure you and your partner take turns picking up items; as soon as one person runs out of ammo, it's hard to get back up to pace.

Survive for 8 minutes or more, and the trophy will unlock upon exiting the end results screen.