I believe Bartemius Crouch Jr. demonstrates the curse by casting it on a spider so intelligence is not required in the books, but this seems like something that might be changed in the fanfic.
Quirrell distinguished himself early on in the fic as saying that the Killing Curse was a spell that solved many problems. He also said (ch 16):
The Killing Curse is unblockable, unstoppable, and works every single time on anything with a brain.
I believe Bartemius Crouch Jr. demonstrates the curse by casting it on a spider so intelligence is not required in the books, but this seems like something that might be changed in the fanfic.
Quirrell distinguished himself early on in the fic as saying that the Killing Curse was a spell that solved many problems. He also said (ch 16):