Here is the full list of all 66 Legion War achievements.
Win a game
Lose a game
Win a game by dragon slayer
Win a game by using Human
Win a game by using Undead
Win a game by using Steam
Win a game by using Wild
Win a game in map Pangaea
Win a game in map Land
Win a game in map Hill
Win a game in map Lake
Win a game in map Island
Win a game in map Continent
Win with hell difficulty
Win with heaven difficulty
Win without recruiting heroes in difficulty hell or higher
Win without losing any units in difficulty hell or higher
Win in 50 turns in difficulty hell or higher
Deal 5000000 damage by units
Deal 800000 damage by magic
Deal 800000 damage by buff
Heal 500000 hp by units
Heal 500000 hp by magic
Heal 500000 hp by buff
Deal 250000 damage for single target
Deal 500000 damage for all targets
Deal 4000 damage for single target by magic
Deal 10000 damage for all targets by magic
Recuirt 2500 units
Kill 15000 units
Recruit 250 heroes
Kill 1250 heroes
Kill 7 units in one hit by unit
Kill 19 units in one hit by magic
Kill 5000 neutral units
Kill 400 neutral ancient units
Kill 40 neutral boss units
Get 10000 equipment
Get 1000 epic equipment
Get 100 legend equipment
Get Emperor Cloth
Kill God of Order
Kill God of Chaos
Get Wine Bucket
Kill Sage
Kill Nobe
Kill Craftsman
Kill Wizard
Become the chosen one
Become the punished one
Get 200000 Gold
Get 200000 Knowledge
Get 200000 Hammer
Get 100000 Mana
Upgrade 400 Knowledge points
Upgrade 400 Hammer points
Create 600 Buildings
Upgrade 1500 Buildings
Get 250000 exp for castles
Get 250000 exp for units
Defeat all 19 waves
Win a game in map River
Win a game in map Center Island
Win a game in map Cross River
Win a game in map Continental Bridge
Win a game in map Big River