Here is the full list of all 12 Fortix achievements. It takes around 8-10 hours to unlock all of the achievements on Windows.
Finish the game on Impossible difficulty.
Destroy all towers (at least 2) on a level with a single capture.
Complete every level to perfect on any difficulty.
Let Xitrof lay 15 eggs on the final level, then win the level.
Capture 100 dragons.
Capture 100 powerups.
Capture Xitrof.
Capture a powerup while you are under the effect of an other powerup.
Capture one of each enemies.
Capture at least 3 triggers with one capture.
Capture a catapult trigger when there is no more turret left to shoot out.
Conquer at least 40% of the playfield with a single capture.