In the anime after kabuto received his sage mode He claimed he was the closest thing to sage of six path. but how close was he in reality?
There's no measured way of saying this, but considering how poorly his control over sage chakra was, because of how much his appearance changed, I guess he was just being arrogant. He wasn't even truly capable of absorbing natural energy, since he implanted himself with cells from Jūgo to absorb natural energy constantly. He also wasn't aware, at that time, of how strong Naruto had become and what his power consisted of, so in summary, he was not the closest thing to the Sage of Six Paths nor he was close to anything like it.