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.
Save the missile silo from the Combine offensive.
Secure the launch doors on missile silo 2.
Send the garden gnome into space.
Defeat the chopper in Episode Two without any misses.
Kill a Combine soldier with his own grenade.
Kill a Hunter with its own flechettes.
Squish every antlion grub in Episode Two.
Find and break every web cache in Episode Two.
Help Griggs and Sheckley hold off the antlion invasion inside the mine shaft.
Kill an acid antlion worker.
Defeat both antlion guards outside the White Forest.
Run over 20 enemies with the car in Episode Two.
Survive the Hunter ambush with Alyx.
Destroy the Combine Autogun in the junkyard.
Find every radar cache in chapter Under The Radar.
Beat DOG in a race to the White Forest base.
Unlock the rocket launcher lambda cache in chapter Under The Radar.
Survive the ambush at White Forest Inn.
Kill 30 enemies with thrown physics objects.
Kill an enemy by planting a hopper mine.
Steal a Zombine's grenade.
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.