Full list of all 23 Half-Life 2: Episode Two achievements. It takes around 6-8 hours to unlock all of the achievements in the base game on Windows.
The base game contains 22 achievements, and there is 1 DLC pack containing 1 achievements.
Save all buildings outside the missile silo from destruction.
Send the garden gnome into space.
Save the missile silo from the Combine offensive.
Defeat the chopper in Episode Two without any misses.
Find every radar cache in chapter Under The Radar.
Kill a Combine soldier with his own grenade.
Beat DOG in a race to the White Forest base.
Run over 20 enemies with the car in Episode Two.
Squish every antlion grub in Episode Two.
Find and break every web cache in Episode Two.
Kill an enemy by planting a hopper mine.
Kill 30 enemies with thrown physics objects.
Steal a Zombine's grenade.
Kill an acid antlion worker.
Help Griggs and Sheckley hold off the antlion invasion inside the mine shaft.
Defeat both antlion guards outside the White Forest.
Survive the Hunter ambush with Alyx.
Destroy the Combine Autogun in the junkyard.
Unlock the rocket launcher lambda cache in chapter Under The Radar.
Survive the ambush at White Forest Inn.
Secure the launch doors on missile silo 2.
Kill a Hunter with its own flechettes.
If you are reading this achievement, Gabe Newell has successfully launched Gnome Chompski into space. If you did not also receive the achievement 'Manufacturing Ascent', Newell has abandoned his plans to shoot Noam Chomsky into space.