Here is the full list of all 20 The Original Strife: Veteran Edition achievements.
Get full stamina and accuracy upgrades
Collect all 3 talismans
Discover all secret areas in a single savegame file
Win a mulitplayer match in 'Capture the Chalice' game mode
Finish game with mediocre ending
Complete the 'Trust No One' demo on any difficulty
Complete the 'Trust No One' demo on Bloodbath difficulty under 6 minutes
Finish game with best ending
Complete the game with best ending on Bloodbath difficulty
Finish game with worst ending
Defeat the Loremaster
Ignite an Acolyte with the flamethrower and have his burning corpse ignite three others
Defeat Macil
Defeat the Oracle
Defeat the Bishop
Defeat the Programmer
Complete the training course
Find the Power Crystal in the Power Station without setting off any alarms
Free the prisoners
Complete Rowan's Mission