I assume it's WA Kabuto.
No restriction ?
Then Kabuto summon his ET army. But Danzo can Koto Kabuto and then it's over (Kabuto will be Danzo's dog and will be forced to cancel ET).
Danzo no diff (you no need eye contact for Koto, so even if Kabuto have immunity to some genjutsu, Koto can still work on him just like Izanami).
If Koto is restricted then Kabuto no diff with ET.
Restrict ET for a more fair fight.
Kabuto low-mid diff.
Kabuto is too versatile, endurant/resistant (with the regeneration of Karin and the liquefaction of Suigetsu). Danzo will surprise him at the beginning with Izanagi and surely a surprise attack but given the reflexes of Sage Mode Kabuto, he won't be totally trolled.
Kabuto will never be immobilized by Danzo's paralyzing seal (in contact). At worst he will use Oral Rebirth.
He will contain Danzo till the end of Izanagi timelimite (11 minutes if we add Shisui eyes) with techniques like Muki Tensei, White Rage and Tayuya genjutsu...
Even Danzo's Mokuton is shit. And Kabuto had developed a poison to neutralize a user of Hashirama cells.
And in the end, without Izanagi, Danzo is murdered.