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