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