Kabuto sure is becoming an asshole after orochimarus death, but then again he was one already so its not much of a difference since he only went from right hand man to master in his plots and this one to use mito sure surprised not only him but everyone and I am sure he was beratimg himself for throwing such a powerful woman fall in narutos hands xD
Anyway kukaku sure is a problem child but so is mirajane who lashes out of heg past jealousy and insecurities but like kiyomi said they will vome around, unfortunately for kukaku it will come with a broken heart as baggage.