Deadly Days
53 Achievements
GOG
Necessary treatment
Heal a survivor that is almost dead.
39.3%
How to unlock the Necessary treatment achievement in Deadly Days - Definitive Guide
GT3OptionFan
TrueAchievements
TrueAchievements
Fairly self-explanatory, but it seems the necessary threshold for healing needs to be lower than just turning the health meter red. My survivor had 7 hp remaining when I healed them and it popped.