Bonus Melee Crit. Mult. determines bonus melee critical hit damage in combat.
For melee weapons and brawling, the game will factor in the Bonus Melee Crit. Mult. whenever a critical hit is rolled, which adds additional damage based on the Ranger's Strength attribute. I.e., on top of the standard critical hit multiplier, the weapon also deals damage based on the melee crit multiplier. Each point of Strength adds 10% to the Damage Multiplier, for a total bonus of 100%.