Here is the full list of all 12 Plenty Karts achievements.
Destroy an enemy kart with Terribly Thick Tar or Placid Pit.
Fired every Plenty Karts weapon in one race.
You won your first Plenty Karts race. Congratulations!
You defeated the first Plenty Karts boss.
Race against your own ghost.
You prevailed against the final boss.
Complete story mode with an engine size of at least 75cc and AI difficulty at least normal.
Complete story mode with an engine size of at least 100cc and AI difficulty at least hard.
Complete story mode with the massive 200cc engine.
Complete story mode with AI difficulty set to expert.
Complete the boss rush on at least medium difficulty and 100cc engine or larger.
Complete the boss rush on expert difficulty and 200cc engine... This can't be done.... There's no way...