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