porschephiliac

This achievement is much easier than it sounds. If you play the 'Air Force One' mission on Easy, it doesn't get much simpler than that.

If you're having trouble, make sure to use your auto-injector often.

To get this achievement, instead of quick-starting an online game, go to custom game, and invite a friend. Once your friend joins you, start the round and finish it and the cheevo will pop.

EDIT: (Thanks to Skelix)

The achievement only works in Ranked Matches. So when you have your friends, make sure your match settings are Ranked, not Private.

All you have to do is play an online game, ranked, to earn this achievement. You have to finish the match in order to unlock it.

Play the game on 'Easy' from start to finish. Acheivements are not stackable for difficulty.

Play the game on 'Hard' from start to finish. Acheivements are not stackable for difficulty.

Play the game on 'Normal' from start to finish. Acheivements are not stackable for difficulty.

This achievement requires you to complete a level without dying, failing, restarting, or continuing on the Normal difficulty.

You must play an entire level in one sitting without stopping the session with death or checkpoint restart, etc... It doesn't matter what mission you choose to attempt this on, all of them are roughly 10-20 minutes long, and equally easy to accomplish. I would recommend, however, attempting this on the first mission, as it is both the tutorial level and intro level to the game. There are plenty of enemies, but if you manage your aim will (Enable Auto-Aim in the options menu) and use cover as often as you can, you will earn this achievement without any trouble. Most experienced FPS players will probably earn this their first try.

The achievement should pop at the end of the level you successfully completed without you having died, failed, restarted, or continued.

EDIT: Might add you need to choose start new campaign. Cannot choose a previously played checkpoint.
(thanks Kennyannydenny)

Message me with any questions.

This achievement requires you to complete the campaign on each difficulty: Easy, Normal, and Hard.

Each difficulty has it's own unlockables, so the order you choose to complete the game is irrelevant. It's logical to start on the easier difficulty first, then progress up from there. At the end of Normal, you will unlock the Hollywood mode, which makes the enemies heads HUGE, as well as the Physics mode, which increases reload time. Enable both of these to make your Hard play through a breeze.

I spent approximately 30-40 minutes on each play through, getting faster every time. I expect one could finish this game in one 2-3 hour sitting if so desired.

The achievement should pop at the end of your 3rd play through if you have successfully completed each difficulty.

Message me for any questions.

This achievement requires you to kill 2 enemy aliens with a single rocket.

About 3/4's through the second level, after you blow the gas station up, you will encounter a flying enemy ship and an available rocket launcher on a highway overpass. You will get about 3 or 4 hits and the ship will fly away to another location. You will run up a set of stairs and you will be able to finish the ship off. At this point SAVE your rocket! You will exit this area, go down a ladder and encounter a few more enemies. After the are finished, you will will be in a tight alleyway. Arm your rocket before you advance. Once you cross the line of the building, 2 aliens pop out. Aim at the ground between their feet and kill them.

If you fail to kill them, and only knock them down, restart to checkpoint. You will have to kill 4 enemies before you can hit these two again. Adjust your aim and fire again. Keep trying, and you will get it. This has proven to be the easier method.

The achievement will pop once they are killed by the rocket. If the achievement doesn't unlock immediately, you did not kill them.

Message me for any questions.

This achievement requires you to survive the story mode to a certain point.

About 1/2-way into the third and final level, you will be tasked with providing cover for Nantz as he holds a laser-designated sight on the tip of the command center. Simply kill all the rushing enemy aliens that try to kill him. After about 90 seconds, a cut-scene will activate and you will watch the tip get rocketed. And then the whole damn thing breaks out the ground.

The achievement should pop during the cut-scene.

Message me with any questions.

This achievement requires you to survive past a certain point in the story and destroy a tanker.

You will be asked to cover Nantz as he runs through the gas station to plant an explosive on a tanker. You will have to kill approximately 30 enemy aliens and monitor Nantz health as he plants the device. I suggest using the available sniper rifle with 'Auto Aim' enabled. Once he plants the device, you will be directed to shoot the gas tank of the tanker.

The achievement should pop once you see the resulting explosion after shooting the tanker. The target will be highlighted.

Message me with any questions.

This achievement requires you to kill 15 enemy aliens with the turret mounted on a Humvee.

At the start of the second level, you will be asked to mount a turret on a Humvee to provide cover. At my best count, there are approximately 20 enemies that spawn here, so kill 15 of them. There is a second turret sequence at the end of the game too, if you unlikely miss it this first time.

The achievement should poop after the 15th turret kill.

Message me with any questions.

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.

This achievement requires you to kill 20 enemies with the available sniper rifle. You will pick up the rifle very early in the first level.

Simply use the rifle and aim for the head or torso and get a kill. Repeat 19 more times. I found it obviously easier to do this on the easier difficulty level - make sure that you do have adequate cover as you aim.

The achievement should unlock on your 20th kill using the weapon.

I earned this achievement in the first level - there are more then enough enemies to kill. Also, if you are having difficulties, make sure you enable 'Aim Assist' in the options menu.

Any questions, feel free to message me.