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.
Disintegrate 15 soldiers by throwing them into a Combine ball field.
Survive the rooftop strider battle in the ruins of City 17.
Kill all of the snipers in City 17.
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 enemies with a Manhack.
Use the antlions to kill 50 enemies.
Play through Ravenholm using only the Gravity Gun.
Use DOG's ball to make a basket in Eli's scrapyard.
Pin a soldier to the billboard in chapter Highway 17.
Kill five barnacles with one barrel.
Break the mini-teleporter in Kleiner's lab.
Escape the apartment block raid.
Get the crowbar.
Get the airboat.
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.
Kill 3 enemies using the crane.
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.
Shut down the supression device by disabling its generators.
Find all lambda caches in Half-Life 2.