I don't know lately. They seem to made Kakashi weaker.
We never seen Kakashi lose in an all out battle.
Pain nope he was still alive he we just messed up he had to watch out for choji and his dad back. I think if he fought pain single handed he would know when to run or think of a better plan.
Itachi and Kakashi he was still standing until they went to leave he dropped.
Kakashi vs Hidan and Haz he was still standing working with weaker people again. Where Asuma failed he stood his grounds good. Until Naruto showed up.
So really we haven't seen him lose 1vs1. But at the same time he wasn't the most unbeatable person we thought at the start of Naruto. I for one at the start of Naruto was like its ok if Naruto messes up Kakashi has a plan.
But at the same time Kakashi never uses all his moves. He might use his eyes, but then he doesn't use his copy cat style, he might use his copy cat style, but he doesn't use his summoings. He never goes all out all out.
I think he is kage material but same time I doubt he could see certain people 1vs1 like the 3rd would.