Board Thread:Theories and Speculation/@comment-26636534-20180125151653/@comment-1872728-20180201022953

Kabuto had Sage Mode, improved with Jugo's Clan's Kekkei Genkai. He also had access to Hyuga, Kaguya, Uchiha, Senju, and Uzumaki Clan's DNA, as well as all the Tailed Beasts' chakra. In my opinion, he could very well be considered the closest thing to Kaguya.