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