Here is the full list of all 50 Viking: Battle For Asgard achievements worth 1,000 gamerscore.
Liberated Galcliff on hard difficulty level
Summoned the dragon-guardian of Galcliff
Killed Hel's Harbinger
Liberated Galcliff on normal difficulty level
Defeated a Legion Giant
Pushed 20 Legion off cliffs to their death
Unlocked 4 advanced combat moves
Achieved victory at the battle of Caldberg
Collected all the skulls in Galcliff
Incinerated 10 Legion soldiers
Liberated Niflberg on hard difficulty level
Collected all the skulls in Niflberg
Completed Viking on the normal difficulty setting
Achieved victory at the final battle for all Midgard
Achieved the perfect victory at the final battle for all Midgard
Powered-up over 500 Vikings using the magic of the runes
Summoned the dragon-guardian of Isaholm
Unlocked all advanced combat moves
Blasted a Legion with Thor's ultimate lightning
Mastered the ultimate ice attack
Demonstrated uncanny deadliness with throwing axes
Isaholm farm, still, lumber mill, and quarry freed from the Legion
Killed 5 Giants
Achieved victory at the battle of Thornvik
Absolutely immolated a Legion
Killed a Legion Champion without being hit
Collected all the skulls in Isaholm
Mastered 12 advanced combat moves
Mastered 8 advanced combat moves
Galcliff farm, still, lumber mill, and quarry freed from the Legion
Executed 100 sneaky kills
Achieved victory at the battle of Holdenfort
Killed 10 Champions
Killed 500 Legion in Midgard
Liberated Niflberg on normal difficulty level
Achieved victory at the battle for Darkwater
Summoned the dragon-guardian of Niflberg
Sneaked into the infested settlement of Darkwater
Performed 150 fatalities
Performed 100 fatalities
Killed 200 Legion in Midgard
Niflberg farm and quarry freed from the Legion
Killed 50 Legion without using a health potion
Defeated a Legion Assassin
Killed 100 Legion
Defeated a Legion Champion
Killed 50 Legion in Midgard
Performed 25 fatalities
Mastered the first advanced combat move
Reach the end of the game on hard difficulty