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.
Find all lambda caches in Half-Life 2.
Play through Ravenholm using only the Gravity Gun.
Destroy six gunships in Half-Life 2.
Discover the hidden singing vortigaunt cave in chapter Water Hazard.
Pin a soldier to the billboard in chapter Highway 17.
Get the Gravity Gun in Black Mesa East.
Destroy the hunter-chopper in Half-Life 2.
Get the crowbar.
Escape the apartment block raid.
Break the mini-teleporter in Kleiner's lab.
Kill five barnacles with one barrel.
Get the airboat.
Get the airboat's mounted gun.
Find the HEV Suit Charger faceplate in Eli's scrapyard.
Use DOG's ball to make a basket in Eli's scrapyard.
Kill 3 enemies using the crane.
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.
Gain command of a squad of rebels in the uprising.
Get through the toxic tunnel under City 17 in Half-Life 2.
Survive the generator plaza standoff in chapter Anticitizen One.
Kill all of the snipers in City 17.
Shut down the supression device by disabling its generators.
Survive the rooftop strider battle in the ruins of City 17.
Disintegrate 15 soldiers by throwing them into a Combine ball field.
Kill five enemies with a Manhack.