Headtaker and Decimator T3 on Damnation with a 4 stack AB 

Since Soulblaze increases the Headtaker and Decimator stack count, with a proper perk (+unarmoured and +infested) combo you can make a 4 stack AB hit like a truck. The trick for Decimator is that you need to have your last melee hit connect with an enemy.
If I manage to find a Decimator IV I am pretty confident this combo would kill every non-elite and non-special in one 4 stack AB. The Dreg Bruisers were left with around 50 HP.