To earn this, you have to face Jeyene in The Spire.
She'll flee and you have to chase her through the Spire.
Eventually she'll face you with 2 of her minions - the key to earning this is to cause enough damage to Jeyne to make her flee, again, whilst leaving behind BOTH of her companions.
I earnt this as a lvl 26 Lucas, with my AI as Reinhardt. It's quite hard to see who is who in the heat of the battle, I looked for Jeynes' distinctive 'spear' weapon, and focused lots of power moves against her before Reinhardt accidently killed on of the handmaidens.
The battle only lasted approx. 40secs, and I did it on my first attempt. Good luck!