Here is the full list of all 15 Gun Skaters achievements.
Play and finish all game types with at least one human player
Kill all players in a round by exploding barrels
Kill 20 players by exploding barrels
Reach level 2
Reach level 12
Reach max level
Shoot players 100 times
Kill 4 zombies at once by an explosion
Reach Round 3 in Zombie Attack
Reach Round 5 in Zombie Attack
Reach Round 8 in Zombie Attack
Clear all rounds in Zombie Attack
Win a football match by scoring 5-0
Play and finish an online match
Win 10 online matches