Here is the full list of all 12 INTERSHELTER achievements.
Kill 5 players in a single round
Commit the first kill in the battle
Kill 10 players in a single round
Kill the enemy that killed you simultaneously
Kill 5 players with batteries in a single round
Escape 11 times
Escape 100 times
Escape 1000 times
Make 3 headshots in a single round
Kill 100 players
Kill 1000 players
Kill 5000 players