Here is the full list of all 26 Eisenhorn: XENOS achievements.
An old adversary dies
Extracted information from the heretic's lackey
Survived a quiet journey on the Essene
Use the soft, cunning ways of the radical
Infiltrated the Glaw's Mansion
Old culture, old families, old poisons
Sneak into North Qualm
Escape the rogue Ecclesiarch
Experienced an untangling of time and space
The bigger they are, the harder they fall
Survive the chaos spawn invasion
Arrive at 56-Izar
Navigate the disturbing Edifice
Complete the game in Easy
Complete the game in Normal
Complete the game in Hard
Complete the game in Extreme
Do a combo of more than 30 hits without breaking the combo window
Do 200 pause for breath attacks
Do 200 Parry attacks
Blind 100 enemies with the psyker power
Kill 100 enemies using take down attacks
Collect all data slates
Reach at least 1000000 coins
Own at least one of each melee weapon
Own at least one of each ranged weapon