Here is the full list of all 11 Pixel Battle Royale achievements. It takes around 0-1 hour to unlock all of the achievements on Windows.
Kill 100 enemies
Kill 90 enemies
Kill 80 enemies
Kill 70 enemies
Kill 60 enemies
Kill 50 enemies
Kill 40 enemies
Kill 30 enemies
Kill 20 enemies
Kill 10 enemies
Kill one enemy