Obtaining the perk
In order to obtain the perk, you must kill any three of the following named marked men: Blister, Beast, Bonesaw, and Blade. You should be able to obtain this easily during the Lonesome Road main quest, unless you are attempting to sneak to get through it.
This perk gives you a bonus of +10% Damage Resistance* and +10% damage against marked men.
Damage Threshold, instead of Damage Resistance. [verified]You receive +10%