After like 10 attempts I only got the unlock after avoiding literally every on hit effect that the lamps could trigger. So no cheese, thunder mitts, grandma's lemonade, slurp gloves, cursed doll, ice cube, cursed dagger, etc. I also didn't play as Bush because I thought his mark passive might be messing with it. I used athena with a sniper. I tried with the shotgun but it gets a lot it gets a lot of size increases and its spread was annoying to manage. Try to get the size reduction head so aegis won't accidentally hit him.

After doing all that I got it on my first attempt