Here is the full list of all 21 Intralism achievements.
Find authors list
Create new level in editor
Up your profile to level 10
Complete level in multiplayer
Play multiplayer match with workshop level
Win multiplayer match
Swich workshop filter in maps list from "trend"
Play 5 maps in relax mode
Play multiplayer game with other player
Play multiplayer game alone
Complete 10 (different) official maps in normal mode
Lose within second after checkpoint and resume from it
Find your items
Recieve your rank
Subscribe to any level in workshop
Launch Intralism
Collect at least one item of each rarity