Here is the full list of all 41 Dark Souls (GFWL) achievements worth 1,000 gamerscore. It takes around 60-80 hours to unlock all of the achievements.
All achievements completed. Congratulations!
Acquire all rare weapons.
Reach "To Link the Fire" ending.
Acquire all miracles.
Discover Gravelord Servant covenant.
Acquire all pyromancies.
Reach "The Dark Lord" ending.
Acquire best weapon through chaos reinforcement.
Acquire best weapon through fire reinforcement.
Acquire best weapon through crystal reinforcement.
Acquire best weapon through lightning reinforcement.
Acquire best weapon through raw reinforcement.
Acquire best weapon through standard reinforcement.
Acquire best weapon through divine reinforcement.
Acquire best weapon through occult reinforcement.
Acquire best weapon through magic reinforcement.
Acquire best weapon through enchanted reinforcement.
Discover Warrior of Sunlight covenant.
Acquire all sorceries.
Defeat Seath the Scaleless, inheritors of souls.
Discover Path of the Dragon covenant.
Defeat the Soul Lord Bed of Chaos.
Defeat Dark Sun Gwyndolin, the Darkmoon God.
Discover Blade of the Darkmoon covenant.
Arrive in Lordran.
Defeat the Soul Lord Gravelord Nito.
Defeat Crossbreed Priscilla, the Lifehunter.
Discover Darkwraith covenant.
Defeat the Four Kings, inheritors of souls.
Acquire the Rite of Kindling.
Acquire the Art of Abysswalking.
Discover Princess's Guard covenant.
Acquire the Lordvessel.
Arrive in Anor Londo.
Discover Forest Hunter covenant.
Discover Chaos Servant covenant.
Ring Bell of Awakening in Quelaag's domain.
Ring Bell of Awakening at Undead Church.
Discover Way of White covenant.
Acquire Estus Flask.
Light bonfire flame.