Combo damage enhancement & Sweeping Attack Enhancement & Heavy Attack Enhancement

Combo damage enhancement*
*: Increase the damage modifiers of the second and third swings by respectively. 

Sweeping Attack Enhancement*
*: Increases the damage of sweeping attacks.

Heavy Attack Enhancement*
*: Increases the damage of heavy attacks (knockdown effect). 


(Gundam: Battle Operation 2 Wiki : Strategy and Mechanics : Basic Mechanics : Melee Directions, Damages, and Combo Damage.) 
I referred to this article.

Combo damage enhancement
Description: Set the first attack damage to 100%. Set the second attack damage to 50% (combo skill required). Reduce the attack damage of the third strike to 25% (Combo skill Lv2 required). This skill increases damage after the second strike.
Increase the damage modifiers of the second swings by X%. The value of X is skill LV x 20. Increase the damage modifiers of the third swings by Y%. The value of Y is skill LV x 60.
LV1=50x1.2=60% ; 25x1.6=40%
LV2=50x1.4=70% ; 25x2.2=55%
LV3=50x1.6=80% ; 25x2.8=70%
LV4=50x1.8=90% ; 25x3.4=85%

Sweeping Attack Enhancement
Description: A skill that increases the damage of sweeping attacks. The standard heavy attack modifier is 80%. Changes heavy attack damage to + X% modifier. The value of X is skill LVx5.
LV1=80+(1x5)=85(%)
LV2=80+(2x5)=90(%)
LV3=80+(3x5)=95(%)
LV4=80+(4x5)=100(%)

Heavy Attack Enhancement
Description: A skill that increases the damage of heavy attacks (knockdown effect). The standard heavy attack modifier is 120%. Changes heavy attack damage to + X% modifier. The value of X is skill LV x 20.
LV1=120+20=140(%)
LV2=120+40=160(%)
LV3=120+60=180(%)
LV3=120+80=200(%)