Most powerful silent killer nin?

[HinataByakuDeath]

I have my hopes up for Minato.

 

[khaoz]

zabuza it was his specialty

 

[HinataByakuDeath]

Seems like you haven't gotten that far yet. Zabuza is great but kakashi surpassed him.

 

[Aaroninja]

Zabuza, Kakashi, probably the other Seven Swordsmen.

I would personally say Muu due to his invisibility and body splitting tech, or Minato due to his speed and Hiraishin