Enduring

From the Comprehensive Rules 4.0:

For each wound on a character with the enduring keyword, that character is strength +2

Some of the most powerful cards with enduring keyword:
9R+48 Sauron, The lord of the rings
10R67 Ulaire Cantea, Thrall of the one
8R38 King of dead, Oathbreaker.

Loaded Keywords
Numeric Damage + X Defender + X Ambush X Hunter X Toil X
Non-numeric Aid Archer Enduring Fierce Lurker Muster Sanctuary Ring-bearer Unhasty
Item Class [Classless] Support Area Armor Brooch Box Bracers Cloak Gauntlets Hand Weapon
Helm Mount Palantír Phial Pipe Ranged Weapon Ring Shield Staff