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