uhm this might just be me but I feel terrible for doppio. He was stuck with diavolo and basically tortured by mettalica. I think diavolo is the real part 5 villain not doppio
In my opinion Doppio didn't even deserved death, he wouldn't have been a villain if Diavolo didn't existed (btw in a certain way diavolo doesn't exist, he's a mental disease, but STILL is passione's bossu, ain't that wacky?)