All the kill achievements:

• The Blessed Dead
  
• Black Seeds of Vengeance
  
• Annihilation of the Wicked
  
• I Whisper in the Ear of the Dead
  
• Slayer of the Gods
  
• Overkill

Kills only count if you complete the level successfully it seems. Whether kills made before continues or restarts are lost is unknown but likely.


Both the medkit achievements:

• The Pills I’ve Took
  
• Slaves on Dope

Most rating achievements:

• Wind of Horus
  
• At the Gates
  
• S.T.A.L.K.E.R.
  
• Working Class Hero
  
• Armed and Dangerous
  
• Quartermaster
  
• Insomniac
  
• Living after Midnight
  
• Constant Gardener

The rest are unachievable without the use of tools. The final level doesn't make a record of your rating to the menu, robbing you of any and all relevant achievements. Laboratories' achievement just doesn't work, even if you somehow manage to glitch a high enough score in the last level of it.

You'll have to restart the game before the achievements that do work actually pop up. Do so after finishing a level if you care about timestamps.

Note, you must achieve a 5-star ranking on ALL the subsections of a level to unlock the level's achievement. Doing them in a row is not necessary so feel free to load up the middle stage if that's the one you failed at.

Everything else. Charming.