Here is the full list of all 67 Warhammer 40,000 : Eternal Crusade achievements.
Reach Rank 4 as any faction
Successfully defend Zedek
Successfully attack Maggon Station
Played at least 20 hours
Successfully defend Olipsis Refinery
Successfully attack Zedek
Successfully attack Torias
Successfully defend Medusa Relay
Successfully defend Imperial Fortress Harkus
Down a Jump Pack character with a melta bomb
Won 10 matches
Successfully defend Pegasus Station
Successfully defend Torias
Successfully defend Maggon Station
Reach Rank 3 as any faction
Successfully defend Blackbolt Defense Station
Successfully attack Blackbolt Defense Station
Successfully defend or conquer a Fortress
Successfully defend Agnathio
Complete any lair mission as a Support Archetype
Complete a mission in under 10 minutes
Kill 10 Tyranids in a single Multikill
Successfully attack Medusa Relay
Reach Rank 2 as any faction
Complete one match
Killed one of the game's developers
Successfully attack Pegasus Station
Successfully attack Olipsis Refinery
Reach Rank 5 with any character
Successfully attack Imperial Fortress Harkus
Reach Rank 5 as a Space Marine
Reach Rank 5 as a Chaos Space Marine
Reach Rank 5 as an Ork
Reach Rank 5 as an Eldar
Kill 1000 Hormagaunts
Kill 100 Termagants
Kill 10 Warriors
Complete any lair mission as a Ranged Archetype
Complete any lair mission as a Jump Archetype
Complete any lair mission as a Melee Archetype
Complete any lair mission as a Heavy Archetype
Complete a hard lair mission as a Ranged Archetype
Complete a hard lair mission as a Jump Archetype
Complete a hard lair mission as an Melee Archetype
Complete a hard lair mission as a Support Archetype
Complete a hard lair mission as a Heavy Archetype
Complete a lair mission with only Ranged Archetypes in your team
Kill a Tyranid Warrior using only personal weapons (Knife or Knuckles)
Complete a lair mission with only Melee Archetypes in your team
Win a battle with a War Party you created
Complete a lair mission with only Jump Archetypes in your team
Collect all commendations as a Space Marine
Complete a lair mission with only Support Archetypes in your team
Collect all commendations as a Chaos Space Marine
Complete a lair mission with only Heavy Archetypes in your team
Collect all commendations as an Ork
Collect all commendations as an Eldar
Successfully attack Agnathio
Earn 5000 XP in a single match for each of the five basic Space Marine classes (XP must be earned on foot)
Earn 5000 XP in a single match for each of the five basic Chaos Space Marine classes (XP must be earned on foot)
Earn 5000 XP in a single match for each of the five basic Ork classes (XP must be earned on foot)
Earn 5000 XP in a single match for each of the seven basic Eldar classes (XP must be earned on foot)
Master all core Space Marine weapons
Master all core Chaos Space Marine weapons
Master all core Ork weapons
Master all core Eldar weapons
Spend 10 AP on Advancements