Six paths is still playable. He is a cheaper version of kakuzu. The name of the game right now is super stacked position 1 and being able to one shot your opponents position 2 to 4. Kakuzu is the best for this task. His standard is AOE along with his chase not to say he can STandard attack twice. Naruto can do the same as well with killer bee, he can standard attack twice. Between the two Kakuzu is the better ninja. He doesn't need other ninjas to scale because he scale through chakra.

Kushina is a tricky cat. Her lack of AOE is a problem but once you are in round 5 and she is alive, you will win the match.