Ascended Winged Knights in One Shot

[Miniature Menace]

As many experienced DS3 players may be aware, one of the best enemies for grinding souls are the three Ascended Winged Knights on top of the Grand Archives. Probably you're already familiar with stacking the Covetous Silver Serpent Ring+3, Shield of Want, Symbol of Avarice, and swapping to the Medicant's staff upon kill to maximize soul gain. But I have another hurdle which, if overcome, might further boost the soul farming rate.

Can you do enough damage to not only kill an Ascended Winged Knight in a single hit, but overkill it to the degree necessary to gain a further souls bonus?

I suspect it might be possible with Hypermode buffs, but I've yet to take that risk. So far, I'm mostly focused on trying to find a weapon with the highest Dark damage possible to boost in a backstab. I know the Blindfold Mask could further enhance this, but it defeats the purpose, because I'd have to swap the Symbol of Avarice out for it. So far, I got the Dark Clutch Ring, the Wasp Ring, a 50/40/40/40 Str/Dex/Int/Faith setup, and the highest damage I've done on a single backstab has been with a Dark Greataxe +10 with both Sacred Oath and War Cry active. I got close to one shotting the Winged Knight, but not quite there. Can this be done without either some variant of hypermode or dumping 20 or more points into Int/Faith? Is there a weapon that deals an even higher amount of Dark Damage on a single hit?