4 tailed naruto?
6 tailed naruto?
KCM mode?
Bijuu mode?
Bijuu Mode > KCM Mode > 6 Tailed Naruto > 4 Tailed Naruto.
4 Tailed Naruto uses power equivalent to the Kyuubi only using 4 tails worth of power i.e. less than half.
6 Tailed Naruto uses power equivalent to the Kyuubi only using 6 tails worth of power i.e. quite a bit above half its power.
KCM Naruto uses power equivalent to the Kyuubi using all 9 tails, however he is unable to use the Kyuubi's maximum potential.
Bijuu Mode uses all 9 tails to its maximum potential.