Here is the full list of all 50 Risen achievements worth 1,000 gamerscore. It takes around 60-80 hours to unlock all of the achievements on Xbox 360.
10 grain plants collected
"Rescue Sara from the wilderness" completed
"Medicine for everyone" completed
"Peace and order" completed
"A package for the Don" completed
"Woman beater" completed
"Power struggle" completed
Find Hemlar's murderer completed
The farmer's sick wife completed
"The test of Master Ignatius" completed
"The sons of Tilda" completed
"The legend of the Gyrger" completed
"The mystery of the eastern temple" completed
"Where is Patty?" completed
"Esteban's return to Harbour Town" completed
"Secure the volcano keep" completed
"The Titan trap" completed
"The fourth seal of rune magic" completed
"Find all the vassal rings" completed
"Find all the teleport stones" completed
"The Inquisitor is dead!" completed
"Defeat the Titan!" completed
First monster killed
Seven grave moths killed
20 wild boars killed
20 chickens killed
500 monsters killed
2000 monsters killed
Rescued the ogre, Drok
250 quests completed
100% achieved in an attribute
Every profession learned
All crystals learned
Every close combat talent learned
Every ranged combat talent learned
100 % achieved in three attributes
Caught by the tideworm 10 times
10 treasures found
Fell to death 3 times
25 Jest spells used
100 locks picked
100 weapons forged
50 pockets picked
1.000 gold coins obtained
100,000 gold coins obtained
300,000 gold coins obtained
Found way out of the first ruin
Found first map in the game
Found first bow
20 tool bags collected in inventory