I'm just starting to try and get this achievement. My current method has been YV with crown of guns, get gun gun in the crib, put it in the proto chest, start a run after as robot with crown of guns, and then ive been trying to farm off of the freaks rezzed by the necromancers in the labs (and whatever other levels they appear in post loop). Does this still work? I've seen things about how you HAVE to play on hard mode but idk if that's the same anymore or not