Malcontent
Escape the apartment block raid.



Trusty Hardware
Get the crowbar.



Anchors Aweigh!
Get the airboat.



Heavy Weapons
Get the airboat's mounted gun.



Revenge!
Destroy the hunter-chopper in Half-Life 2.



Zero-Point Energy
Get the Gravity Gun in Black Mesa East.



Hallowed Ground
Escort Gregori safely through the church cemetery.



Where Cubbage Fears to Tread
Defend Little Odessa from the gunship attack.



Warden Freeman
Survive the second turret standoff in Nova Prospekt.



Follow Freeman
Gain command of a squad of rebels in the uprising.



Radiation Levels Detected
Get through the toxic tunnel under City 17 in Half-Life 2.



Plaza Defender
Survive the generator plaza standoff in chapter Anticitizen One.



Fight the Power
Shut down the surpression device by disabling its generators.



Giant Killer
Survive the rooftop strider battle in the ruins of City 17.



Singularity Collapse
Destroy the Citadel's reactor core.

Lambda Locator
Find all lambda caches in Half-Life 2.


I reuploaded this video to fix any mistakes :)



One Man Army
Destroy six gunships in Half-Life 2.


This Achievement isn't that hard to get as long as you kill every gunship you come across!
There are 3 in chapter Highway 17.

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There is 1 in the beginning of chapter Sandtraps and 2 together at the end.

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Chapter 1: Point Insertion


Submissive
Put the can in the trash.


or alternatively,


Defiant
Hit the tashcan cop with the can.


Instead of putting the can in the trash throw it at his face


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Chapter 2: "A Red Letter Day"


What cat?
Break the mini-teleporter in Kleiner's lab.


Keep teleporting the cactus back and forth, eventually it will break and you will get this achievement


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Chapter 3: Route Kanal


Barnacle Bowling
Kill five barnacles with one barrel.


You can get this achievement on Chapter 2: Route Kanal, send an explosive barrel down this pathway and shoot it when they've grabbed it and it's almost all the way up.


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Chapter 4: Water Hazard


Vorticough
Discover the hidden singing vortigaunt cave in chapter Water Hazard.


Make sure you have plenty of health as you'll need it.

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Chapter 5: Black Mesa East


Blast from the Past
Find the HEV Suit Charger faceplate in Eli's scrapyard.


Stack up a box so you can jump up onto this ledge, up there you'll find the charging faceplate

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Two Points
Use DOG's ball to make a basket in Eli's scrapyard.


Use the gravity gun to shoot a hoop with DOG's ball! This achievement is actually pretty hard and will take a few goes, atleast it did for me.


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Chapter 6: "We Don't Go to Ravenholm..."


Zombie Chopper
Play through Ravenholm using only the Gravity Gun.


This is my speedrun of Ravenholm! I tried to go as fast as possible, if you're struggling just take it slow and try and keep one of the circular blades with you at all times.

Chapter 7: Highway 17


OSHA Violation
Kill 3 enemies using the crane.


When you get in this crane in chapter Highway 17, 3 combine soldiers will come out of a garage, just swing things at them until all 3 are dead and you should get this achievement!




Targetted Advertising
Pin a soldier to the billboard in chapter Highway 17.


On this little hill in Highway 17 you can pick up the crossbow, immediately after picking it up you can scope in and shoot this soldier on the billboard in front of you and you'll get the achievement.


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Chapter 8: Sandtraps


Keep Off the Sand!
Cross the antilion beach in chapter Sandtraps without touching the sand.


In chapter Sandtraps there is a part where if you touch sand you spawn antlions, get from one side of the beach to the other without touching the sand to get this achievement! Here is my video if you need any help.



Bug Hunt
Use the antlions to kill 50 enemies.


When you kill the large antlion you get it's pheropod, you can throw this at enemies and it will spawn antlions that will kill them, do this 50 times and you'll get this achievement



Chapter 9: Nova Prospekt


Flushed
Kill an enemy with a toilet.


At the start of Nova Prospekt in one of the cells is a toilet, pick it up with the gravity gun and hit the first enemy you find, this will get you the achievement.


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Hack Attack!
Kill five enemies with a Manhack.


I think the easiest chapter to get this achievement on is Nova Prospekt, you can grab the manhacks with your gravity gun and shoot them at combine soldiers


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Chapter 11: "Follow Freeman!"


Counter-Sniper
kill all of the snipers in City 17.


To get this achievement you need to kill all 5 snipers in City 17, on Chapter 11. I used grenades in my video but the rocket launcher also works!
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Chapter 12: Our Benefactors


Atomizer
Disintegrate 15 soldiers by throwing them into a Combine ball field.


In chapter 12: Our Benefactors when your gravity gun goes blue it gives you the ability to pick up enemies and throw them around, this is a good place to get the achievement throw all the combine soldiers into this wall of ball fields.

I will be updating my guide with the Episode 1 & 2 achievements when I have time.
However if you have already previously completed the achievements for Episode 1 & 2 you can unlock them for free. Just install the original Episodes, (they are hidden in the 'Tools' section of your steam library) then launch it. Afterwards close the game and launch Half-Life 2 and the new achievements will unlock.

I have a full achievement guide for Black Mesa you can find here:
https://gtm.you1.cn/sharedfiles/filedetails/?id=2303703792