Most badass unexplored character?

[MinaButt]

Sakumo maybe.

 

[Tobi98]

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This guy, they way he blocked that leafs nin sword was awesome, his wind sword was one of my fave attacks, I was sad we never got to see it again.

Yeah I thought he was going to do something in 1st part of the war but oh well

OT: Another one is Ao, killed and took the eye of a Hyuuga, Kage body Guard, 1 of the best sensors fought Shisui and made him use KA

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[Bad Touch Yakushi]

MANGETSU HOZUKI

has to be known

 

[Multiply]

Genma is a god among kage. He was too powerful to be a kage himself so he had to pretend he was weak and protect Minato.

 

[RicardoA]

I can't say there's only one because Naruto has dozens of background characters who had tons of potencial, but sadly Kishi didn't bother developing them at all (ex: Konoha's jonin and tokubetsu jonin are the first i can think of).
That's one of the things that annoys me in this manga.

 

[ultraChalk]

Genma and Kakashi's dad.