I unlocked this by accident but reckon doing so I've stumbled upon a very repeatable method. The reason is it only requires one enemy rather than two.
Chapter 9 is a very short level where you fight a 'boss', the last captain.
Their path is always to walk slowly towards you. When getting close, they execute a special move that cannot be interrupted and deals damage all around them.
So when you start the level, go forward and shadow jump up (
) through the gate to get to the fight. Skip the cinematic (
) and jump forward and to the left, so you're in the shaded area. Once there, break the light orb and then let the captain get close enough so they spot you, whilst preparing to blink behind them. Quickly jump when it's clear they have seen you and turn around. You may need to wait a split second for them to trigger their special move or not, depending how late you left it to jump, but get close and stab them in the back with
. As killing them doesn't interrupt their move, they will kill you as you kill them.
Given I got it without trying when I first messed up, I believe it should be fairly easy to time it right. I repeated a couple of times after and it wasn't tricky at all, but you may need a couple of restart. If that is the case however, given there is no setup and this fight is at the start of the level, it shouldn't be too much trouble.