Uchiha.. Shisui.. An important Uchiha that benefitted two shinobi who became average to OP all because of him. Itachi became invincible just by possessing Shisui's eye until using it on himself and saving himself and many other shinobi from Edo Tensei. I mean it was all thanks to Shisui for giving Itachi his eye. But only Itachi seemed to have gotten the credit. U_U
It is also theorized that Obito may have used Kotoamatsukami through Shisui's eye from Itachi in order to build trust with him so that the Uchiha Clan Massacre could be initiated. Obito may have used Kotoamatsukami on the 4th Mizukage as well as the Kyubi around the same period with the help of Senju Cells implanted within him thanks to Madara Uchiha.
Danzo was also OP having gained possession of not only Shisui's eye but also of his arm, a number of sharingans and Senju DNA giving him plenty of chakra, allowing him to use Izanagi and Kotoamatsukami number of times within a day. Yah, Danzo Shimura is another character who is unappreciated. He lost all because of Plot no Jutsu otherwise he probably would've been as strong as Itachi and Madara. hmm
