Now before I'm called a fap boy read the op pl0x.
Sage Mode techs are the only thing that can hurt him in my opinion this isn't really a weakness since he tanks sage mode techs better than the whole Naruto verse.
He walked off a sage Rasengan and continued to battle like it was nothing. Everyone who would be hit with that would more than likely die. The way how I see it it's not a weakness, but the only thing that can hurt him.
If that makes sense.