Here is the full list of all 30 Hyper Knights: Battles achievements.
Spawn 50 Space Ninjas
Play a Battle with 4 Units in the same Team
Play at least 1 Battle in every map
Play a Battle between Ogres and Shielders in the Castle
Play a Battle between Archers and Ogres in the Wilderness
Play 5 Battles in the Coliseum
Play a Battle with over 500 Archers
Play a Battle between Minions and Shielders in the Coliseum
Create an Animation
Create a Unit
Stun 2000 Units
Kill 1000 Units
Play 10 Battles
Play a Battle between Spartans and Persians in the Hot Gates
Play a Battle betwen Chuck Boris and 100 Minions
Play a Battle between Archers and Marines
Play a Battle between Marines and Chickens
Play a Battle between Marines and Spartans
Play 5 Battles in the Hot Gates
Stun 500 Units
Play your first Battle
Play a battle with 2 or more custom Units
Kill 5000 Units
Play 5 Battles in the Castle
Upload a Unit to the Workshop
Create 10 custom Animations
Play 5 Battles in the Wilderness
Play 5 Battles with 2 Custom Units
Play 50 Battles
Kill 10,000 Units