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