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