File contains 2 folders: Malignant and Sneaky achievement game save files, both during NG+ playthrough.

Malignant :
Chapter IV Protector’s Duty - section 6 (The mass grave of the marshes).
In order to get the achievement, simply stick for that particural section with 33-66% kills, which should be total of ~6 enemies killed, no matter how you do it. Once you pass through the "door", this should count toward opportunism skill, thus unlocking the achievement. I thnik that 2 guards that are killed by the crossbow at the beginning,counts toward that total number. 

Sneaky :
Chapter IX Tales and Revelations - section 4 (Entering the Sanctuary).
In order to get the achievement, simply just be sneaky. In that section you are not able to kill or alert guards anyway. Once you pass first doors and get the scene of passing over the mountain ledge, you should get the experience toward rudence, before going to the 2nd part of the section. If the first time does not work, then completing the whole section should do the trick. 

FEW DISCLAIMERS:
1) MAKE A BACK UP OF YOUR OWN GAME SAVE FILES JUST IN CASE. 
2) This is NG+
3) Actually I think that moving just Sneaky files and then doing chapter sections IV for Malignant and then getting back to chapters and going into IX for Sneaky should work, but I didn't test it out, thus including both files. 
4) Game text may be in polish so you'd need to change that, unless you don't care. In that case the Chapters you are looking at, in polish are:
a) Rozdział IV - Obowiązek Opiekunki - 6. Masowy grób na bagnach
b) Rozdział IX - Opowieści i odkrycia - 4. Wejście do sanktuarium 
5) It's a steam version, so the game save file location was for me in \Steam\userdata\userid\1182900
6) It may take a while for your cloud to synchronize the file, but it works after a while. 
7) Just enjoy the "mod" if it works and I'm happy I could save you some hours if you do not like the grind.