Le jugement divin est impartial

This achievement requires you to chain 5 kills in a row using Acherons technique. The game counts two consecutive kills as a chain as long as Acheron does not leave the greyscale effect that occurs when you use her technique. Find a location with 5 enemies and begin mashing your technique button, ensuring that you do not stop in order to keep her within the greyscale state until all 5 enemies are defeated.