Here is the full list of all 19 Planetary Annihilation achievements.
Build every kind of unit
Kill a commander within five minutes, five times
Use more than 95% of the metal and energy you produce in a match
Start a game with a custom system
Watch competitive play for eight hours as a spectator
Manage your armies with all ten control groups
Keep tabs on your conquest with ten camera anchors
Watch competitive play for two hours as a spectator
Build every kind of basic factory
Annihilate your opposition throughout the galaxy
Discover a new loadout in galactic war
Activate an annihilaser
Win against three times as many players
Eliminate a faction in galactic war
Participate in ten team games
Destroy five enemy planets with annihilasers
Smash five enemy planets
Target an incoming planet with an annihilaser
Build every structure in a single game