Here is the full list of all 67 Warhammer 40,000 : Eternal Crusade achievements.
Down a Jump Pack character with a melta bomb
Successfully attack Blackbolt Defense Station
Reach Rank 5 with any character
Reach Rank 5 as an Ork
Successfully defend Blackbolt Defense Station
Played at least 20 hours
Successfully defend Torias
Successfully attack Pegasus Station
Successfully defend Olipsis Refinery
Reach Rank 4 as any faction
Successfully attack Maggon Station
Win a battle with a War Party you created
Successfully attack Imperial Fortress Harkus
Successfully defend Agnathio
Successfully defend Zedek
Successfully attack Olipsis Refinery
Successfully attack Agnathio
Successfully defend Imperial Fortress Harkus
Successfully defend Medusa Relay
Won 10 matches
Successfully attack Zedek
Reach Rank 3 as any faction
Successfully attack Torias
Successfully defend Pegasus Station
Reach Rank 2 as any faction
Successfully attack Medusa Relay
Complete one match
Successfully defend or conquer a Fortress
Successfully defend Maggon Station
Killed one of the game's developers
Reach Rank 5 as a Space Marine
Reach Rank 5 as a Chaos Space Marine
Reach Rank 5 as an Eldar
Kill 1000 Hormagaunts
Kill 100 Termagants
Kill 10 Warriors
Kill 10 Tyranids in a single Multikill
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 Support 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
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
Complete a mission in under 10 minutes
Collect all commendations as an Ork
Collect all commendations as an Eldar
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