Here is the full list of all 52 Lone Fungus achievements.
Collect all Relics
Collect 75 Mindshrooms
Learn everything you can from the Grand Librarian
Collect all Emblems
Open all levered one way gates
Listen what the Professor Statue has to say about each mushroom cap
Talk to every Major Statue
Collect all Health Crystals
Read all the 'Ten Commandments' tablets
Use the Bouncy Spore Spell to reach somewhere higher up
Collect all Spell Stones
Learn both Great Slashes
Acquire the Spark Ball Spell
Complete the game (True Ending / Selfish Ending)
Forget the past, reincarnate only the Greencap culture of mushrooms (Selfish Ending)
Unlock the Royal Ornament
Collect all Brain Nodes
Leave the Kingdom (Abandonment Ending)
Unlock all Bounce abilities
Acquire the Vibrant Crystal Spell
Collect 50 Mindshrooms
Acquire the Golden Light Spell
Cut 1000 Flowers/Flora
Acquire the Returning Contraption Spell
Unlock the Fire Bounce ability
Acquire the Spicy Nut Spell
Acquire the Berserk Spell
Unlock the Teleportation Wand
Unlock the Spin Jump
Unlock the Wall-Bounce ability
Acquire the Acid Hammer Spell
Collect 25 Mindshrooms
Unlock the Crouch Jump ability
Defeat 500 Enemies
Collect 4 Health Crystals
Acquire the Bouncy Ball Spell
Acquire the Bouncy Spore Spell
Acquire the Boost Projectile Spell
Unlock both the Dashes
Defeat 100 Enemies
Learn how to Conjure a Mushmover
Unlock the Mushmover Infusion ability
Collect all Ladybugs
Parry 200 Projectiles
Downward Slash the Bouncy Spore 5 times in a row without touching the ground
Fullfill your destiny on the 'Normal' Difficulty (True Ending)
Fullfill your destiny on the 'Hardcore' Difficulty (True Ending)
Fullfill your destiny on the 'Nightmare' Difficulty (True Ending)
Collect all Astral Fragments
Achieve 100% completion and finish the game (True Ending)
Achieve 100% completion and finish the game on the 'Nightmare' Difficulty (True Ending)
Fully upgrade your sword's damage