yamamoto is massively hypersonic. hes the fastest character in bleach in a universe where soi fon was zipping around so fast she was creating afterimages. thats dragon ball level (not z) speed.so he can win by simple speedblitz and shoving his sword in narutos throat.
second way he can win. kidou. basic kidou can shut down movement entirely like when byakuya stopped rukia with one spell. once that happens he can walk up to naruto and just slap him repeatedly.
third way he can win. soul crush. no one in narutoverse has reiatsu like yama does not have chakra. but reiatsu crush affects even normal humans with no spiritual energy. it disintegrates them just by being NEAR a high powered shinigami like yama. yama has to put a seal on himself to go down to the human world so he doesnt destroy everything by existing
his destructive capacity is large city level, possibly planet level given his bankai hype. madara's katons are like NOTHING compared to bankai yama
he can swamp naruto with millions of dead skeletons.
he can shikai him into dust
final way he wins: intelligence and experience. yamamoto is MILLENIA old. hes been in COUNTLESS battles.
edit: i know who he is... isn't he the head captain in Gotei 13?
he just spams a few flames... for show.
you couldnt be more wrong about yama ji. he has been captain for a thousand years and not once was someone stronger than him born in that time
incinerated by yama's shikai flames
you have to be fukin high if you think yama ji is gonna be speedblitzed by anyone in naruto
defensive protection via cloak shield
can it tank the sun?
reiatsu crush. kidou