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.
Get the airboat's mounted gun.
Discover the hidden singing vortigaunt cave in chapter Water Hazard.
Destroy the hunter-chopper in Half-Life 2.
Find the HEV Suit Charger faceplate in Eli's scrapyard.
Get the Gravity Gun in Black Mesa East.
Use DOG's ball to make a basket in Eli's scrapyard.
Play through Ravenholm using only the Gravity Gun.
Kill 3 enemies using the crane.
Pin a soldier to the billboard in chapter Highway 17.
Destroy six gunships in Half-Life 2.
Cross the antlion beach in chapter Sandtraps without touching the sand.
Kill an enemy with a toilet.
Survive the second turret standoff in Nova Prospekt.
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.
Find all lambda caches in Half-Life 2.
Escape the apartment block raid.
Break the mini-teleporter in Kleiner's lab.
Get the crowbar.
Kill five barnacles with one barrel.
Disintegrate 15 soldiers by throwing them into a Combine ball field.
Gain command of a squad of rebels in the uprising.
Kill five enemies with a Manhack.
Use the antlions to kill 50 enemies.
Get the airboat.