How to get 10HP heal with medikit
Solution 1:
- The basic Medikit heals 4HP.
- The Improved Medikit foundry project adds an extra 2HP.
- The Savior skill (Colonel-level option for Support) adds an extra 4HP.
All of these together give a total of 10HP per heal.
As noted in the comments, in Enemy Within there's also a medal that can add 2HP to heals received by the wearer - so a Support Colonel with Improved Medikit could heal a wearer of that medal for 12HP.