Here is the full list of all 33 Half-Life 2: Update achievements. It takes around 8-10 hours to unlock all of the achievements on Windows.
Defend Little Odessa from the Gunship attack.
Escort Gregori safely through the church cemetery.
Get the Gravity Gun in Black Mesa East.
Discover the hidden singing vortigaunt cave in chapter Water Hazard.
Destroy the Hunter-Chopper.
Get the airboat's mounted gun.
Get the airboat.
Get the crowbar.
Escape the apartment block raid.
Hit the trashcan cop with the can.
Survive the rooftop strider battle in the ruins of City 17.
Cross the antlion beach in chapter Sandtraps without touching the sand.
Destroy the Citadel's reactore core.
Survive the generator plaza standoff in chapter Anticitizen One.
Play through Ravenholm using only the Gravity Gun.
Shut down the supression device by disabling its generators.
Get through the toxic tunnel under City 17 in Half-Life 2.
Survive the second turret standoff in Nova Prospekt.
Break the mini-teleporter in Kleiner's Lab.
Disintegrate 15 soldiers by throwing them into a Combine ball field.
Find all lambda caches in Half-Life 2.
Find the HEV Suit Charger faceplate in Eli's scrapyard.
Gain command of a squad of rebels in the uprising.
Kill all of the snipers in City 17.
Kill five barnacles with one explosive barrel.
Use the Antlions to kill 50 enemies.
Kill 3 enemies using the crane.
Kill an enemy with a toilet.
Use Dog's ball to make a basket in the scrapyard.
Pin a soldier to the billboard in the chapter Highway 17.
Put the can in the trash.
Destroy six gunships in Half-Life 2.
Kill five enemies with a Manhack.