Bless Unleashed

In order to get this achievement you need to kill an enemy with a gear score warning. I can't seem to paste just the icon but if you check this page you'll see the two icons.

https://support.blessunleashed.com/hc/en-us/articles/3600361...

If you highlight a quest and it shows this icon with a number it means the enemies are a high enough level above you to be above your gear score. There are few instances in this game, which means every enemy spawn is a free-for-all. The good news is just doing damage to an enemy is enough to allow you to get experience and loot, and also credit for this achievement. When I reached the first big city I took the west exit and went south, you'll find a bunch of mushroom enemies and human enemies fighting each other to your left, just south of a telepost. This is where I got it. There's usually a lot of people fighting enemies there, so just attack an enemy someone else is killing and you should get credit for it. Note there's a "quest" for that pass thing for killing GSW enemies (12 I think) so perhaps this would be a good place to do it.

I haven't tried it, but I assume you could equip shit equipment to lower your gear score and get it that way if you're already high level.

PSYCHADELICACE confirmed you can unequip your stuff (aside from weapon) and kill something your level.