Yeah shisui have too many bugs, he can get 10 attacks without receiving any debuff (on my server shisui users saying thats "normal" and its not bug...) but in arena he is beatable you just need to nuke him before he can do his standards in 1st round, in non arena battles - well good luck :D

There were always at least 1 OP ninja but never that much OP that he has no counter...