Kill 1,000 zombies in a row without taking damage while solo in Cursed Tier 3
PSA: for anyone considering going for this, or for anyone put off even trying it thinking it will be too difficult, if you lose your overheal HP from Light Mend, this seemingly does not fail the challenge!
I got to 700 kills, then a Zursa spawned and its bees took my overheal down from 400hp to 397hp. But 300 kills later I completed the challenge!
This probably means you could take up to two hits from a zombie without failing it. It might work with overheal from Stim Shots too.