This is a late question but while I do think ive seen all of buffy I havent seen all of angel or even the multimedia involved with the franchise like the books and games and frankly idk how much of that is even considered canon but from all of that was it ever revealed if there is a being or even object that can kill glory while she is in her real form and not through the ben form, im just curious if such a thing was said to exist.

Cause from what I gather from what ive seen from the franchise here is who I could see possibly able to kill glory as she is:

Buffy with that spell in season 4 finale that I guess gave her the power of her pack against adam

Dark willow

The circle of the black thorn combined cause I do recall angel saying as a whole they are unstoppable or almost unstoppable

Angel infused with marcus blood

I think there was an episode of buffy with a genie so maybe someone could wish glory to be dead.

Unfortunately as much as I'd like to put them here I cant put the master, the mayor, turok han, caleb, connor, illyria, marcus as powerful as they are I dont think they would kill glory in a fight.