Here is the full list of all 33 Half-Life 2 achievements. It takes around 12-15 hours to unlock all of the achievements on Windows.
Pin a soldier to the billboard in chapter Highway 17.
Discover the hidden singing vortigaunt cave in chapter Water Hazard.
Use DOG's ball to make a basket in Eli's scrapyard.
Get the Gravity Gun in Black Mesa East.
Find the HEV Suit Charger faceplate in Eli's scrapyard.
Destroy the hunter-chopper in Half-Life 2.
Get the airboat's mounted gun.
Get the airboat.
Break the mini-teleporter in Kleiner's lab.
Disintegrate 15 soldiers by throwing them into a Combine ball field.
Shut down the supression device by disabling its generators.
Survive the generator plaza standoff in chapter Anticitizen One.
Get through the toxic tunnel under City 17 in Half-Life 2.
Gain command of a squad of rebels in the uprising.
Kill five barnacles with one barrel.
Escape the apartment block raid.
Get the crowbar.
Play through Ravenholm using only the Gravity Gun.
Kill 3 enemies using the crane.
Destroy six gunships in Half-Life 2.
Cross the antlion beach in chapter Sandtraps without touching the sand.
Use the antlions to kill 50 enemies.
Kill an enemy with a toilet.
Survive the second turret standoff in Nova Prospekt.
Kill all of the snipers in City 17.
Survive the rooftop strider battle in the ruins of City 17.
Find all lambda caches in Half-Life 2.
Kill five enemies with a Manhack.