Aliens: Colonial Marines

Stand against a Xenomorph and kill it with a shotgun.

Kill a Xenomorph thats attached to the walls or ceiling.

Experience is earned from kills, collectables, completing challenges, match bonuses and campaign chapters completed.

Simply reach rank 2 as a Marine to unlock.

You get challanges as you play the game, complete anyone of them to unlock.

Simply change your Marine loadout found at "versus", "edit loadouts", "marine loadouts" for this achievement.

Kill 10 Xenomorphs that are coming out of vents on the roofs or walls.

Look out for the dog tag collectables as you play the game, collect one for this achievement.

Unlocks when you've finished the first mission

Collect a legendary weapon to unlock this achievement.

When a Facehugger jumps at you you wil grab onto it, simply throw it away from your face to unlock.

Unlocks when you've finished mission 3 (Sulaco Falls).

When a Xenomorph grabs your partner, simply free him from the alien's attack.

Set up a UA 571-C Remote Sentry - part of the story.

The M56A2 Smart Gun can be found in Mission 4, simply get 10 kills with it to unlock. You can restart the checkpoint if needed.

Unlocks when you've finished mission 5 (The Raven).

You must kill 2 Xenomorph enemies, the human enemies does not count. Easiest way to get this achievement is to kill 2 Xenomorphs with the underslung grenade launcher from the pulse rifle.

Unlocks when you complete mission 8 (Rampart).

Best done in 1vs1 match with a friend, or the spitter aliens can be found in mission 6. Simply use a long range gun to kill them without being hit. If you are hit, restart from checkpoint.

Unlocks when you complete mission 9 (Hope in Hadley's).

Complete mission 7 without anybody setting off any alarms.The very first scientist will spot you and set off an alarm. This is inevitable, but won't influence the achievement.

Unlocks when you've finished mission 11 (Home).

Complete the game from start to finish.

Simply track 100 targets on your Motion Tracker to unlock.

Revive your co-op partner in a co-op match to unlock.

Newt's doll can be found in mission 5 (The Raven)

Complete the end of mission 3 (Sulaco Falls) under 2:30 minutes to unlock.

Experience is earned from kills, collectables, completing challenges, match bonuses and campaign chapters completed.

Simply reach rank 20 as a Marine to unlock.

Have another player join your game.

Melee attack a Lurker alien that's jumping towards you. Works in single player and multiplayer.

Simply change your Xenomorph loadout found at "versus", "edit loadouts", "Xeno loadouts" for this achievement.

The earliest you can unlock this achievement is when you reach level 18 for your marine. Upgrading the combat pistol is probably is the easiest weapon to get this with. It has 3 upgrades needed for the achievement

Towards the end of mission 9 (Hope in Hadley's) there is a fight with a crusher. Once it appears, find high ground to avoid damage from it. Kill using your explosives and shooting the body. You must get the kill for this to count. Use restart checkpoint to your advantage if you're damaged by it or don't get the kill. Can also be done in a multiplayer game.

Collect all 6 legendary weapons in the game. These are:

Level 1- Hick's Shotgun
Level 4- Gorman's Pistol
Level 5- Hudson's Pulse Rifle
Level 6- Vasquez's Smart Gun
Level 9- Vasquez's Pistol
Level 10- Frost's Flamethrower

The earliest you can unlock this achievement is when you reach level 18 for your marine. Upgrading the combat pistol is probably is the easiest weapon to get this with. It has 3 upgrades needed for the achievement. A weapon skin is also needed.

This achievement unlocks when you finish the campaign on Veteran difficulty

These look like small laptop computers and highlighted in a light blue color when you're close. Collect all 12 to unlock.

Commendations are the points you receive to purchase upgrades with. These are earned each time you rank up.

Early in mission 2, keep an eye on the walls to find a keypad.When you use it, it will unlock a door you recently passed that was locked. Once you enter this room, the achievement will unlock.

Clear every campaign mission on Ultimate Badass, the hardest difficulty - and you can pick it from the start, no need to beat the game first. Far easier in co-op (solo, your AI squadmates are near useless), and the campaign's short, so bring a strong loadout (pulse rifle/smartgun) and grind through. You can mission-select to clean up any levels.

Defeat the Raven in under 1:10 minutes on Soldier difficulty or higher. If you're struggling, pause and select "restart checkpoint" to try again

The Firebomb is unlocked at rank 4. Kill 3 alien enemies with a single bomb to unlock. Human enemies does not count for this achievement.

Collect all 35 dog tags found in the game. One of the dog tags was glitched and had to restart from checkpoint to unlock but this achievement is unlockable.