When they killed Anya off unduly
Anya had some ups and downs over the course of her tenure on “Buffy,” having started out as a vengeance demon before becoming human, then going back to being a vengeance demon, then back to human. But she was a great character nonetheless, and if we were to have to choose anyone to die in the final battle, it wouldn’t have been her. It probably would have been Xander, tbh.