Kakuzu takes this mid difficulty.
Kakuzu's
You must be registered for see links
, not internal organs except for his heart so I doubt the internal damage that Gai's blunt hits can cause will actually do much damage to Kakuzu. Not when
You must be registered for see links
right after
You must be registered for see links
. This goes to show that Kakuzu has a high tolerance of pain so Gai's taijutsu won't harm Kakuzu.
As for Hirudora, the air pressure caused by
You must be registered for see links
may very well nullify it thus Gai will expend a lot of energy using Hirudora whereas Kakuzu won't have. If Atsugai can't nullify Hirudora, it can still reduce its impact so Kakuzu can tank it with doton domu when Kisame, whose durability isn't as hyped as Kakuzu's and was in a
You must be registered for see links
prior to his bout with Gai,
You must be registered for see links
even without Samehada healing capabilities. Even after getting hit by Hirudora,
You must be registered for see links
which is why
You must be registered for see links
. Even after that punch, Kisame managed to break
You must be registered for see links
and then
You must be registered for see links
so Kakuzu with domu isn't getting killed by Gai's strongest and most chakra taxing attack let alone his weaker ones.
Anyway, Kakuzu isn't going to let Gai use Hirudora and can attack him while Gai is
You must be registered for see links
prepping the attack.
Furthermore,
You must be registered for see links
survived
You must be registered for see links
so Gai's regular punches can be tanked by those masks who can then entrap Gai within those threads or counteract with elemental jutsu. Gai isn't breaking out since Kakuzu managed to trap Chouji, Ino and Kakashi and considering Chouji himself has superhuman strength, I doubt Gai's strength surpasses the three of them's. Those threads are noted to be very
You must be registered for see links
so they can definitely interrupt Hirudora which took quite a few pages to hit Kisame since when Gai was first starting to prep it.