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