Ugh, I dont want to use George Foyet for this unsub in this sotry but seriously, the original Reaper (not even the second incantation in Omnivore and definitely not the one who was all Hotch-centric and vengeful) was an awesome ass unsub. Plus his being a hebephile and handy with knives fits exactly who this character is in the AU.
And Raphael Hankel (who happens to be one of my favorite unsubs *Don Swayze fuck yeah*) doesnt really because he was just a religious zealot and child abuser. He may have been a murderer too but I dont remember, I dont think so. So I may just have to go with Foyet. He’s not the biggest bad guy in the story but the idea of a showdown with Sam where Sam comes out on top, is always appealing.