well well...u think kakashi is a genius???kakashi destroyed two hearts of kakuzu....1st one when kakuzu was bind to shikamaru's shadow mamic...second one when naruto had hit him wid his rasen shuriken and he was at the brink of heart failure...at that time he could have been killed by even konohamaru...

....as far as pain was concerned so kakshi never was thinking that pain can come back...he did try to destroy tendou by using raikiri by couldnt....so why didnt using kamui???he also had no idea while fighting pain that pain is controlled by nagato ...the code was later broken by shikamaru and shizune...so stop giving kakashi credit like he is a genius...he always goes for kill but just cant kill...