@Jackhng I Agree. Boro was really powerful because his virus would kill before they find out that he has a core, and even if they do both Boro and the opponent will die, unless the fight is to one sided (meaning they are many leagues above Boro). Science and maybe Otsutsuki dna is the only counter to Boro's virus. Btw I would just like to mention that in that fight:
The Karma Bothers were both = Low/Mid Kage Level, Adding Sarada's Sharingan and herself/base Mitsuki who were High Jonin/Low Kage Level dependent on what stage of the fight. Then considering their combined abilities, hax and team work which made them way stronger puts them near the top in High Kage Level.
So ya they aren't some fodder Chunin kids who folded Boro, because they can beat most (not all) of the Akatsuki. I'd argue that Karma Kawaki alone is Stronger then anyone who is bellow Kisame.
