Here is the full list of all 24 Fear Effect Sedna achievements.
You took Glas's side at the end of the game
You took Hana's side at the end of the game
You didn't take a side at the end of the game
You got through Hell
Kill Rain stealthily in Hana's Hell
Restore 75% of your health with the life steal of Atiqtalik
You survived Atiqtalik's wrath
Read every document in the game
Kill 50 enemies stealthily
You saved Glas, but not Rain...
Complete the puzzle of the Tanker in 7 actions
Complete the level of the boat's deck without being detected
You discovered strange experiments
Kill 50 enemies with skills
Kill 3 enemies with a single turret of Glas
Draw the attention of 20 enemies with the lure of Rain
Kill 50 enemies with the tactical pause
Kill 3 enemies with a single bouncing bullet of Hana
Kill 20 enemies with the burn damages of the flamethrower of Deke
Make an enemy kill their ally with the confusion of Axel
You learned more about inuit mythology
You recruited new teammates
Complete the gala without taking more glasses on the buffet
You began the adventure