So here is an interesting idea. Heat and energy have this stat, why not physical? It would basically reduce maximum health (no surprise there). *rest of post no longer relevant*

Isn't Max Health damage just HP damage..? xD

What this does is limits the maximum amount of health you can have, from health kits and the like. This means that if you use it when the enemy has less than 20 health missing you essentially get a damage bonus. For example, let's say you have an attack doing 50 damage and 10 max health damage. Using it when the enemy has a max health of 500 will effectively do 70 damage (it damages them to 450/480 health, equivalent to 430/500).

It will be only useful when in 1v1 and when the opponent could "repair kit to max HP in beggining of the battle" (bad move) xD