Here is the full list of all 12 Rabbids: Party of Legends achievements worth 1,000 gamerscore.
Get 2500 or more for 'Hatched From Stone Eggs' (FFA).
Get 8000 or more for 'The Gold Crown-Fitting Ceremony' (2V2).
Get 4500 or more for 'Where The Foul Winds Blow'.
Get 5000 or more for 'Fiery Bumper Karts' (2V2).
Get 8000 or more for 'The Venomous Escape' (2V2).
Get 6000 or more for 'Feeding King Yellow Brows' (2V2).
Get 7000 or more for 'Dance Battle By The River'.
Get 6250 or more for 'Punishing Palms'.
Get 5750 or more for 'Who Is The Real Monster?'.
Get 7000 or more for 'The Bull Fight'.
Get 5500 or more for 'Angry Great White Turtle'.
Get 8000 or more for 'Counting Rabbids'.