Whether or not the anal was rape or not, Chantal automatically gets / got an "I Spit On Your Grave"-style revenge on Nader as soon as he commits the act. Can you imagine getting your dick anywhere near Chantal's ass, never mind plunging it straight up her asshole?
That thing is never scrubbed, never soaped, never washed, never wiped, is encased in never-laundered unbreathable fabric for days on end, has weeks of backsplash all over it, is subject to roaring cases of diarrhea, likely has crusty patches of hair surrounding it, doubtlessly leaks septic anal fluid regularly, and is located right near her vaginal opening, which is an entirely separate world of should-be-illegal horrors not even worth describing right now.
Unless Nader has a predilection and kink for fucking abandoned Port-A-Potties, it's hard to say who's getting it worse in this whole Satanic ritual.