You will encounter the sisters in two areas of Hell, in the first encounter rather than fight them directly, they will Bring King back to life as a cyborg.
You can cheese through this encounter by taking the shock grenade and max out the use of weapons skill tree so you regain energy during ranged attacks. Throw a grenade, shoot the boss and grenade again, if performed correctly the cyborg is unable to move at all.
After you've depleted his health, the sisters will then revive him, simply repeat the stunlock and he will go down for a second time. Yet again the sisters will revive the cyborg for the third and final time, stunlock him to his final death. The sisters will leave and you'll continue to follow them, eventually leading to a direct engagement.
For this fight, You'll see a pod located in the center of the room, this will be your main source of damage negation throughout the fight as the sisters will use the same attack the Mother Unit has used in your previous encounters. Energy shield is not needed as you will use the pod in the center of the room to stand behind and wait out the energy beam so spend them elsewhere to gain an advantage.
Around the pod you'll notice more Angels and corpse piles, in order to reduce the host spawns in the first phase you will need to burn these quickly, the Angels themselves cannot be killed so don't waste time attempting to finish them.
Phase two is much like phase one with no change in boss abilities or attacks - the only difference is that the unkillable Angels will periodically spawn hosts, just take these out and continue as you did throughout the first phase, the sisters will go down, and your trophy will pop.
