Here is the full list of all 31 Idle Clans achievements.
Smith a piece of Astronomical armour
The true test for any respectable chef... Make a pizza.
Reach max level in a skill
Purchase the most glamorous property available
Create a godlike item
Reach level 100 in a skill
Steal from the royal clan
Create a clan
Defeat a boss
Join a minigame
Grow some watermelons
Battle a monster with an Outstanding weapon
Achieved upon reaching your first million
Receive a boss key
Purchase your first property. It's nothing to brag to your parents about, but it's a start.
Eat a burger in battle
Enchant an item
Purchase an upgrade
Defeat a dragon
Equip diamond jewellery
List an item for sale
Create silver jewellery
Send an item to your clan's vault
Join a clan
Refine an item
Prepare a special dish
Perform a leaderboard search
Plunder a small, helpless village
Your first level up
Complete the tutorial
Reach a billion gold