it was a good battle when Gaara first fought him but i think Gaara has improved, and i may be the only one who thinks this but i think he would have beat deidara if it had not been in his viilage too much distractions....and im just going off what i've seen and using the information i know, yes i know he beat all three Sanin and gave them that name but in a one on one fight there's not many people who can beat Kakashi...for example, so many people think Kakuzu was good, but if you watch the fight kakashi killed him like twice i think...if he had one heart the fight would have been mad short, also when Kakashi was fighting God Realm Pain, he almost killed him but he moved anothe pain in the way before it happened. i know he cant beat all six but Kakashi is by far the smartest and careful fighter in naruto. so yea i think he could beat Hanzo in a One on One fight...Kakashi biggest weakness is he runs out of chakra really fast...so if you gave him naruto's, nobody would be able to stop him.
-But on a serious nobody really knows when it comes down to it,it's all on comparing what little you know and seen, im pretty sure if i post Jiraya can beat Madara people would say Madara...but how do we really know, its called a Debate thats all we do, i explain why i think team pain would win and why i think Kakashi would win against hanzo...back up your reason..