The biggest Asspull that Kishi pulled to me is..
Ginkaku and Kinkaku being able to live in Kurama's stomach by eating the flesh from Kurama's stomach. Inside Kurama's stomach is uncooked meat soaking in stomach acid that should have killed them. They should've died of dehydration because there's nothing to drink in Kurama's stomach but his stomach acid. I think it's the biggest ass pull of the entire manga.