this.. it isn't dangerous as long as it is well proportionned(?)
if naruto would use senjutsu without using an equal portion of chakra, the balance would be offset and the sage mode would dissapear.
if he took too much senjutsu and if he took too little it would take over his body and turn him to stone

so the rasengan he used must have been pure nature chakra, it also explains why he did it whilest gathering nature chakra.. he had to create it whilest gathering or else it would offset his balance to create one!
you guys dont understand sage mode. naruto cant control how much nature energy he takes in, that is why you need massive amounts of chakra to use sage mode, because you cant control how much you take in. when naruto enters sage mode, he lets his body absorb nature energy, and he has to balance that nature energy with his own spiritual and physical energy to enter sage mode, thats why you need enourmous amounts of chakra. if you could control how much nature energy you take in, people without massive amounts of chakra would be able to use sage mode, hell if you could control the intake, anyone could use it. but you cant control it, hence needing massive chakra reserves. nature energy + physical energy + spiritual energy = senjutsu chakra.
and i dont really understand what you are trying to say about the rasengan...english please. naruto didnt create the rasengan at the same time as him absorbing nature energy. he sat there absorbing nature energy, went into sage mode, and then made a rasengan right after he went into sage mode...like he has done a million times in the past. the rasengan was not pure nature energy. it was senjutsu chakra. it was narutos physical energy + spiritual energy + nature energy = senjutsu chakra, then he used that senjutsu chakra to make the rasengan. so the rasengan was physical energy + spiritual energy + nature energy. regular chakra is just spiritual energy + physical energy by the way. you take those two and mold them together into regular chakra. sage mode is just thlse two parts plus nature energy, then you mold those three together into senjutsu chakra. there is no way to just use nature energy, you cant mold one type of energy into chakra. the reason why it worked against obito is because the juubi is made up of nature energy, so therefore obito is made up of the same thing now, so it stands to reason the only thing that can harm the juubi/obito is the same thing its made of.
also the thing with pain has nothing to do with anything, yes pain absorbed narutos sage mode rasenshuriken, but that wasnt pure nature energy he absorbed, it was molded senjutsu chakra, like i already said, is physical energy+spiritual energy+nature energy, it was already molded into chakra when he absorbed it, he wouldnt turn to stone since hes not just absorbing pure nature chakra. when the path grabbed naruto and was sucking narutos chakra out directly from naruto, he turned to stone then because naruto started absorbing pure nature energy, therefore pain started absorbing nature energy, and since pain doesnt know how to balance the three energies together, physical/spiritual/nature energy, he turned to stone because the nature energy wasnt balanced. that doesnt happen when he just absorbs a jutsu already molded into senjutsu chakra.
Clearly but some how it still made his body weak for some reason... Tobirama said it wasen't completely erased
Ik im just saying Naruto can't use sm in his jutsu... Preta Path absorbed Sm Naruto and Jiraiya Rasenagn without any effect...
tobirama said it wasnt erased, meaning the jutsu gamakichi used wasnt turned to "dust" like every other jutsu used against obito up until that point. amaterasu, rasenshuriken, sandaimes shuriken kage bunshins, etc., were all turned to nothing, obito "erased" them from existence. gamakichis water blast though wasnt erased, he just blocked it with a sort of barrier, but it didnt disappear. thats all tobirama meant...it didnt do anything to obitos body at all.
so you are saying that only naruto or the 1st hokage could kill obito?
yes, from the info we know so far, it looks like only naruto and hashirama can damage obito, since they are the only ones who can enter sage mode so far.