These challenges are meant to be ones you can only do in versus multiplayer, but you can actually get a few of them in the campaign mode. As Aliens: Colonial Marines does not have a splitscreen option for versus multiplayer, you will need to have an online connection to get many of these challenges.
"Purchase a xeno combat upgrade."
You will need to play as an alien and reach rank 2. Once you get to this, you will be able to purchase one combat upgrade, which you can get in the xeno loadouts menu. Purchase anything to complete this challenge.
"Win an Extermination mode match."
Extermination mode has you trying to destroy alien eggs when playing as a marine, and protecting them from marines when playing as an alien. Keep playing the extermination mode until you win one match. How long it takes just depends on how skilled the team you are with is.
"Win a survivor mode match."
Survivor mode has you and a team of marines holding out against a team of aliens. If a marine dies, they do not respawn, but the aliens will keep respawning. The marines have to hold out until the timer ends, whilst the aliens have to try and kill all marines before the timer ends. Again, like the previous challenge, this one just depends on how skilled you and the team you are on is.
4) ESCAPE ARTIST
"Win an Escape mode match."
The escape mode has a team of marines trying to reach an evac point, whilst a team of aliens tries to stop them. Once again, this challenge depends on your skill and your team's skill. Just keep playing until you win once match.
|"Remember when people use to fear us rather than laugh at us? I miss those times."|
"Kill 25 enemies in Team Death Match."
Kills made whilst playing as either a marine or an alien count towards this challenge, so if you got 15 kills as a marine in the first round of a match, then 10 kills as an alien in the second round, it will unlock. Note that you have to be playing in the team death match mode, the other modes don't count towards this challenge.
6) RAKING CLAWS
"As a Soldier Xeno, kill 10 enemies with Quick Strike."
Quick strike is an upgrade you must purchase for the soldier xeno. Once you have it, you'd probably be best playing some team death match to get this. The quick strike is a fast attack, so try and find a lone marine and then quickly move in make the kill.
7) SPIT IN YOUR EYE
"As a spitter Xeno, kill 10 enemies with Acid Spit."
The spitter's acid spit lets it attack enemies from a distance. You can also charge up this attack, making it more powerful and more likely to kill in one or two hits. Hold back and if you see a group of aliens fighting a group of marines, start spitting at them -you'll most likely get a kill picking off weakened marines.
8) CAT-LIKE REFERENCES
"As a Lurker Xeno, pounce on three enemies in less than 10 seconds."
A lot of people have moaned about this challenge, but it isn't actually anywhere near as difficult as it sounds. What you need to purchase is the "speed pounce" for the lurker xeno, something you can get once you've reached rank 14. Then when you're in a game, try and find a lone marine (team death match mode is probably your best bet) and sneak up. The speed pounce will only knock over an enemy, rather than pin him like the other pounces do. The best part is that as the marine gets back up, you can speed pounce them again, and then again, to unlock this challenge -it doesn't matter if it is the same enemy pounced, it still unlocks.
9) HEADS UP
"As a xeno, kill an enemy from the wall of ceiling."
Start crawling across a wall of ceiling, and try and fine a marine. Whilst on a wall of ceiling, the alien's attacks will change, such as it using tail-whip attack which can kill an enemy in a couple of hits. If you're struggling with this, try and hide nearby the special weapons the marines can pick up, such as the RPG, and then quickly kill them before they collect the weapon.
10) SENTRY DUTY
"Destroy 5 sentry turrets."
You can only get this as playing as the alien in the survivor or escape modes. The marines can use sentry turrets, but they will obviously try and set them up in places where the aliens won't be able to attack them without being blown apart. To make things worse, the sentry turrets are pretty sturdy, and take several hits to destroy. And if you try and attack one, there is a fair chance a marine will kill you. You'd probably be best trying to get this one in the escape mode, as the maps aren't enclosed spaces like the survivor maps are. And as the marines need to progress to win, sometimes the players playing as marines will leave the sentry guns behind (picking up and carrying a sentry turret really slows a marine down). So once the marine team starts moving forward, hang back and let the other aliens fight them. You can then go back and hopefully destroy the sentry turret.
11) TWO BIRDS...
"Kill two enemies with one shotgun blast."
This can be achieved in single player. There seems to be a glitch with this challenge, as a lot of people have had it unlock for them despite not meeting the requirements. Right at the start of the second mission, two guys will run through a door. I got this one here. Try to shoot them as soon as they run in, as they're fairly close to each other.
"Track 50 xenos on the Motion Tracker."
This is another one you can do in single player. Whenever you get into a big battle -such as the one in the vehicle bay in "Hope in Hadley's" -just keep looking at your motion tracker occasionally.
13) BLUNT FORCE
"As a Soldier Xeno, kill 10 enemies with Heavy Strike."
The heavy strike is an upgrade you need to purchase for the soldier xeno. Once you have it, go into any multiplayer mode (team death match is probably the best mode) and get some kills. The heavy strike is a very powerful attack, which usually kills a marine within two hits.
|"If you watch this scene in Alien, doesn't it totally look like I'm slowly ballroom dancing with an invisible partner?"|
14) HAWKED IT ALL UP
"As a Spitter Xeno, kill 2 enemies at once with a single fully charged Spit attack."
To get this legitimately would take a lot of skill and luck. I can only suggest trying to find some marines who are already weakened, and are standing very close to each other -obviously something that probably won't happen often. And even if it does, it takes a few seconds for the spitter to fully charge up the spit attack (hold down the button), so another alien will probably move in and get the kills. This was one challenge I had to boost for. When boosting, strike the two marines three times each, then quickly charge up the spit attack and fire. Aiming for the legs seems to work better than aiming anywhere else.
"As a Spitter Xeno, kill 10 enemies with Acid Rebound."
Acid rebound is a combat upgrade you'll need to purchase for the spitter xeno. Once you have it, play some team death match and get some kills with it. The acid rebound is a spit attack which can bounce off walls and floors, allowing you to hit enemies you can't even physically see.
16) KILL 'EM WHILE THEY'RE DOWN
"As a Lurker Xeno, kill an enemy after knocking him down with Speed Pounce."
You have to purchase the speed pounce for this one, which requires you to have reached rank 14. Once you have it, use the speed pounce to knock a marine down -it won't pin them, but as they get back up, use a strike attack to tear them apart as they get back up.
17) FIRE IN THE HOLE
"As a Marine, kill 25 Xenos using the Smart Gun, Flamethrower, or RPG."
These are all special weapons you can find in multiplayer maps. However, you can also get this in single player -if you play through "No Hope In Hadley's", you'll get access to a smart gun around halfway through the mission, and will have to work your way through some sewers which has a ton of aliens in it.
"As a Soldier Xeno, kill 10 enemies with Flurry."
The flurry attack is another upgrade you'll have to buy. Once you have it, go into team death match and get some kills with it. The flurry is a series of quick strikes which will quickly kill a marine, so get up close and attack.
19) STEPPED IN IT
"As a Spitter Xeno, kill 5 enemies with Acid Trap."
The acid trap is yet another upgrade you'll have to purchase for the spitter xeno. This attack has the projectile stick to walls and will then explode if a marine gets to close to it. For example, if you aim at floors, the projectile will explode when a marine walks over it. You can also aim directly at a marine and it will hurt them.
20) SHOCK AND AWE
"As Lurker Xeno, hit 2 enemies with a single Shockwave Pounce attack."
You'll have to purchase the shockwave pounce upgrade. Once you have it, you are probably best going into an escape mode match, as the marine players are more likely to stay close to one another. When the alien lands from this pounce, it sends out a shockwave which can knock over marines who are within the radius of it. In the "Emergency Evac" map in escape mode, try and get this when the marines are waiting for the elevator to come near the start, as they have to wait in a small space which makes them easy targets.
21) HARD BOILED
"As a marine, kill 5 Xeno Boilers during a multiplayer match."
The xeno boilers are the white aliens. The alien players can only use them after a certain amount of time in the match has passed. To make things worse for the marines, they have a lot of health and can kill you easily with their powerful acid. Plus with all of the other aliens running around trying to kill you, it can be difficult to take them out without being killed yourself first. Try and pick one off at a distance with the pulse rifle's grenade launcher -it takes two direct hits to kill them with this. You do not have to kill 5 boilers in one match, the count is collected over multiple matches.
|"What were they thinking with some of these challenges, really."|
22) EXTENDED REACH
"As a Lurker Xeno, kill 5 enemies using Lunging Strike."
The lunging strike has to be purchased before you can use it. This strike has the lurker alien move forward quickly before attacking, and the strike itself does a decent amount of damage. Try using the speed pounce to knock over a marine, then move back as they get back up. Then use the lunging strike.
"Kill 8 enemies with acid damage."
Using any of the xeno spitter's spit attacks will count towards this, and you can pick off marines at a distance to make it nice and easy.
24) MERCY KILLER
"Use the Combat Pistol to kill 5 enemies that were covered in fire."
Another challenge that you can get in single player. Actually this is much like the "Combined Arms" challenge, only you actually have to kill less enemies. This is easier to do against aliens, as they are more resistant to fire than the human enemies. Use the assault rifle's incineration unit to light up some aliens, then quickly switch to the combat pistol and start shooting. Upgrading the combat pistol so it has an extended magazine and the full-auto option helps.
25) LEFT A MARK
"As a Spitter Xeno, kill 10 enemies with Acid Strike."
Acid strike has to be purchased before it can be used. Once you have it, pick the spitter xeno, play some team death match and gets some kills. The strike does more damage than the regular strike.
26) TRAP SPRUNG
"As a Marine, kill 25 Xenos using Claymore mines."
Even though you can use claymores in single player, you can only unlock this challenge by playing multiplayer. Once you've planted a claymore, you'll need an alien to walk towards it and it will explode when it gets close. One claymore can often kill an alien closely, but you can only ever use one once per life. So after your claymore has explode, what do you do? You walk towards the nearest wall, and then fire to pulse rifle's grenade launcher to blow yourself up. Then once you've respawned, you'll have another claymore, so plant it and repeat. Bonus points if your team mates get super pissed at you like mine did!
27) FLURRY FINISH
"As a Lurker Xeno, kill an enemy with a Claw Flurry after a Speed Pounce."
Bother the claw flurry and speed pounce have to be purchased before they can be used. Once you have them, play a team death match game and try to sneak up on a lone marine. The speed pounce will knock them over, so tear them apart with the flurry as they get back up.
28) SLICED AND DICED
"As a Soldier Xeno, kill 2 enemies with a single Whirlwind attack."
The whirlwind attack is another combat upgrade you'll have to purchase. This attack has the alien spin around and use it's tail to hit enemies near it. If a marine has full health, it takes two whirlwind attacks to kill them. So killing two with one attack is just a case of being in the right place at the right time. Ideally you'll want to find two weakened marines who happen to be close to each other, then quickly run in and strike them down.
"As a marine, kill 5 Xeno Crushers during a multiplayer match."
The xeno crushers are the large aliens that the alien team can use after a couple of minutes have passed in the match. You will most likely only ever be able to kill two of these per match, if you're lucky -the crushers have a lot of health and can kill you instantly. And of course, if you are solely targeting the crusher, the other alien players can pick you off easily. The crusher can be hurt more easily from behind, so if you see it going after other players, move in and start firing with the pulse rifle's grenades, or better yet, try to find the RPG if it is available.
|"You may hate this game, but if the DLC has achievements, I'll bet you buy it."|
30) ACID BATH
"As a Spitter Xeno, kill 10 enemies with the Rupture mutation."
You have to purchase the rupture upgrade before you can use it. This is actually a really easy challenge, as all you need to do is get as close as possible to a marine. When they shoot and kill you, the xeno will explode with an acid shower, which is practically guaranteed to kill any marines next to it.
31) FREE HUGS
"As a Lurker Xeno, kill 20 enemies using the Pounce attack."
The pounce attack will pin a marine down, and then have the lurker xeno slash them apart. However, other marines can shoot you off, so try and use the pounce against lone marines.
32) EASY PREY
"As a Soldier Xeno, kill an enemy after stunning him with the Bludgeon."
The bludgeon has to be purchased before it can be used. This attack will stun an enemy, so once you've hit someone with it, quickly finish them off with any other attack to unlock this.
33) FROM THE SHADOWS
"As a Lurker Xeno, kill 5 enemies without taking any damage."
This one is very difficult to do without boosting. You don't have to necessarily do it in one match (e.g. kill 3 enemies in one match, then 2 in the next) but even so, this is one of the toughest challenges in the game. Have the pounce equipped, and try to quickly sneak up on lone marines and make the kill with the pounce, as they won't be able to fight back if you hit them.
"As a Xenomorph, kill 5 marines without dying."
This one depends on your skill. If you're struggling, you could try waiting until the xeno crusher becomes available to use, as the crusher has a lot of health and can also kill marines instantly.
"As a Marine, kill 5 Xenos without dying."
I found this one easier than the alien's equivalent of it, as you can just hang out with your fellow marines and as you've all got guns, you can attack at quite a distance. If you are having problems with this challenge, try and find the smart gun, if it is available -this gun has auto tracking and can easily blow apart other aliens, so you should be able to get a few kills with it as long as you keep the aliens at a distance. But it doesn't have much ammo, so make every shot count.
36) HARD TO KILL
"Complete an Escape match without being incapacitated."
What this means is you need to finish an escape mode match as a marine without ever being downed. This also means you must fully complete the match (as in get to the very end and escape). It doesn't matter if any of the other marine players are downed, just as long as you aren't. So try and stay close to your team mates, pick up all the health and armor items you can get, try and make your way through the map quickly and keep the aliens at a distance. This last challenge is all dependent on your own skill. Although it also helps greatly if the alien team has bad players in it.
|"Are you finally done? Then quick, trade the game in now! You've only got a few more minutes until it drops to the $1 bargain bucket!"|