karin didn't run out of chakra while healing sasuke or tsunade, she
You must be registered for see links
and
You must be registered for see links
respectivily.
You must be registered for see links
like she did with sasuke(maybe healing wounds and just transferring chakra work on different scales(which makes even more sense when you facter that she bites herself to heal)).
With the chakra tsunade got from karin she healed to the point of reattaching her body and recovering her youth, then she heals the other 4 kage and then she
You must be registered for see links
and matched kn0 byakugou sakura to the point that they were running out of chakra at roughly the same time, despite healing an army well into the 10s of thousands. Mind you tsunade with years worth of byakugou chakra turned into a old hag after pain's attack, and this was sakura with 3 years for of chakra. Couple that with the fact that the main use of the 100 healing in this case was to
You must be registered for see links
the
You must be registered for see links
of
You must be registered for see links
being
You must be registered for see links
from by the
You must be registered for see links
and if thats not enough we can just look at kabuto's
You must be registered for see links
. Unless youre gonna pick hairs and say a tenacious lifeforce isn't synonymous with large amounts of chakra.
In Fact we've never seen karin run out of chakra and even when she didn't get the chance to heal and restore sasuke completely he was still able to use chadori twice on panel fight kakashi to a stand still, bust out v3 susanoo, and attempt to go v4 b4 blindness took him.
Her reserves aint nothing to scoff at.