Every Warframe players knows that melee combat is the way to dish out the most damage possible in the shortest amount of time. While some folks cry foul on balance issues, melee being super strong leads to some fun times in Warframe, but the system is also complicated and filled with nuance.
The basis of the melee system is the Combo Counter. Each successful hit against enemies within a brief will cause the combo counter to increase. Upon achieving a certain number of hits, a damage multiplier is then applied. This multiplier does not impact regular melee strikes, but is instead applied to Heavy Attacks when they are performed.
If enemies are not hit for 5 seconds, the Combo Counter will reset to zero, although both the duration before reset and the Combo Count earned with each strike can be impacted by the correct mods.
The bonus damage to Heavy Attacks is 2x after 20 hits, with an additional 1x being added every 20 hits after that to a maximum of 12x. Remember, this multiplier only applies to Heavy Attacks.
When Combo Efficiency is a factor is at the moment the Heavy Attack is unleashed. A Heavy Attack will normally use 100% of the stacked hits to gain 100% of the applicable damage multiplier, but modding for Combo Efficiency allows players to keep some of the stacked hits, while still getting the benefit of the total stack multiplier.
So, 220 stacked hits will yield a 12x damage multiplier. This can then be unleashed with a Heavy Attack, but if the player has a Combo Efficiency of 50%, only 110 stacks will be used to generate the 12x damage multiplier. Combo Efficiency can be achieved through Mods, or certain Focus Schools such as the Zenurik tree’s Inner Might node.