Battle: Los Angeles

This is towards the end of the first mission, you get to a pool and then two aliens will attack you. One on the roof and the other right in front of you. You cannot miss this achievement, so dont worry about this one :)

This achievement is story related; you cannot miss this achievement.

Shortly after the first cut scene in the first level you will go through a building and exit it coming up to an empty pool. An alien will jump out of the pool in front of you. Kill him and the one on the building above you and the achievement will unlock.

This achievement requires you to survive past a certain point in the story. Approximately 3/4's through the level, you will encounter a hotel with a swimming pool. As you approach the pool, an enemy alien will jump up out of the pool and another will spawn on the nearby right-hand-side rooftop. Kill both of these enemies.

The achievement should pop after you kill both enemy aliens.

Message me if you have any questions.