I just finished the Cursed Court cursed chest event, and the achievement doesn’t update.
Is this achievement finicky and won’t update unless you get the double chest reward?
Finished it with 89 creatured killed within the time limit and got one chest reward.
Edit; With a bit of luck, the event chest spawned on one of the next couple of spawns of Cath lvl 2, and I managed to get 100 kills before the timer went off. This time the achievement stuck.