Without Kurama, this is what he loses:
- A large supply of chakra. Without Kurama, there is no natural mixing between his own chakra and Kuramas, which means he cannot make clones regularly and spring back because of the healing quality and resilience Kurama naturally provides his body.
- That means people can forget that he trains through SM and Rasangan quickly. In fact, he wouldn't even have an FRS, which is useless anyways without Kurama's chakra.
- He hasn't learned SM because he cut down the time yet again.
- People can forget mass clones.
Even if I do offer him the courtesy of SM, then he's mid Jounin at most. Because he has what, like one technique at his disposal bar Kage Bunshin? Yeah, that's where he lies; Rasangan and KBs.
Also, let's see the common things Naruto can do with Kurama's chakra:
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- Kurama being the source of Naruto’s stamina.
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With Kyuubi connection: Naruto resisting poison.
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Without Kyuubi connection:
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Not to mention the mass clones.
My answer: A bit stronger than Nagato but weaker than Sasuke
I changed my answer.
I hope to God you are joking.