Here is the full list of all 34 Stardust Defenders achievements.
Defeat the Matriarch of the corrupted spiders.
Defeat the Ultra Fungus, the boss of all mushrooms.
Defear the Ultra Snail, mother of all evil snails.
Defeat the Ultra Beetle, the boss of all corrupted creatures.
Defeat 1500 spiders.
Defeat 7500 spiders.
Defeat 25000 spiders.
Defeat 1000 fungus.
Defeat 5000 fungus.
Defeat 15000 fungus.
Defeat 1000 snails.
Defeat 5000 snails.
Defeat 200 beetles.
Defeat 600 beetles.
Win the game with the Guardian of Greenery.
Win the game with the Solar Gardener Guardian.
Win the game with the Sorcerer Supreme Guardian.
Win the game with the Frost Burst Guardian.
Win the game with the Star Summoner Guardian.
Win the game with the Storm Guardian.
Win the game with the Fiery Fury Guardian.
Gain 1 million Stardust units.
Win the game with the Life Points at 100%.
Reach level 10 in the Offensive Magic upgrade.
Survive 7 minutes with 20% or less of the Life Points.
Reach level 10 in any Guardian's upgrade.
Reach level 8 in the Persistent Magic upgrade.
Reach level 8 in the Mana Recharge upgrade.
Reach level 10 in the Orb Control upgrade.
Reach level 10 in the Flowering upgrade.
Reach level 8 in the Desperate upgrade.
Reach level 10 in the Flaming Stars upgrade.
Reach level 10 in the Blooming Sunflowers upgrade.
Reach level 10 in the Empowered Amulet upgrade.