Does Kunais Count As swords If they do i pick the 4th hokages also by sword i will have to say Kisames sword Sameahada or orchimarus even though he is dead.
Itachis Susanos Sakenagi Longsword is defintely the most powerful but aside from that one iw ould say the Samehada but In other situations a sword such as silent killing, the Decapitating Carving Knife is much better suited
I think they are all situational. I really like kisames sword, just for the fact that people who fight it tend to think its just a crazy sword. Not realizing that its eating all their chakra, but then its too late as he finishes them off lol.