Here is the full list of all 25 12 orbits achievements.
Arena: Play a whole game against 11 opponents without ever being eliminated. No modifications.
Unlock all other achievements
Orbs can be a little shy sometimes
Multiball: Destroy all three of one team's goals within 12 seconds
Arena or Trails: With 2 or more players, color 50 spheres before a single player is eliminated
Trails: Hit 2 players with a single shot
Blizzard: Win a 1 vs 6 match while controlling no one but the solo player. No modifications.
Skip the countdown to start a new game in less than a second
Trails practice: Score 35 points with a single player and without ever touching a wall
Arena Practice: Score 26 points with a single player and without ever orbiting
Blizzard practice: Score 28 points with a single player
Blizzard practice: Score 20 points with a single player and without ever dodging
Orbit with 12 players at the same time
Blizzard practice: Score 16 points with a single player
Blizzard practice: Score 22 points with a single player
Trails practice: Score 25 points with a single player
Trails practice: Score 37 points with a single player
Trails practice: Score 50 points with a single player
Finish a game with an active modification
Use a single blast to trigger two more blasts
Color 12 spheres with a single blast
Arena practice: Score 40 points with a single player
Arena practice: Score 30 points with a single player
Arena practice: Score 20 points with a single player
Hit the player responsible for your elimination with one of your own spheres, before it becomes their color