Here is the full list of all 21 Rock of Ages 2: Bigger Boulder achievements.
Win a match of War without letting the enemy touch your door.
Defeat the Dragon without losing any boulders.
Defeat The Thinker without losing any boulders.
Destroy the enemy boulder using the thundercloud.
Defeat the Sphynx without losing any boulders.
Win the match against God without letting him score any goals.
Get a bronze medal in all time trial levels.
Get a silver medal in all time trial levels.
Get a gold medal in all time trial levels.
Win an online match of War.
Win an online match of Obstacle Race.
Win a match of War using only animals to defend (cows, whales, lions, bulls or elephants).
Cross the Dragon's sea once without falling into the water.
Destroy the castle doors using the Block of Ages.
Collect all the stars from the story campaign.
Land in the highest scoring hole in the Skee-Boulder ramp.
Earn the Squire's medal by climbing up in the ranking system.
Earn the Knight's medal by climbing up in the ranking system.
Earn the Lord's medal by climbing up in the ranking system.
Earn the King's medal by climbing up in the ranking system.
Earn the High King's medal by climbing up in the ranking system.