The most efficient Masskiller

[tunechisan]

B with his crazy sword handling

 

[Guildmage]

definitely mei, sasuke survived because he had susanoo on and zetsu helped him, but if mei increased the PH level to the point of instant meltdown she would have melted even the people on the other room, but now that she doesn't has to worry about anyone? instant meltdown to thousands of shinobis= 0.01s finish battle =) =)

 

[tiptop]

1)naruto- 100 shadow clones - then 100 rasenshurikens from all of them
2)sasuke- amaterasu spam - fry them bitches !!!!
3)sixth paths of pain - use common sense

 

[Tosen]

Nagato enough said

 

[Owarij]

sasori destroyed nations with his puppets, nagato self explanatory, deidara bomber

 

[arv993]

muu is a good choice too.