All we know is Shisui has the greatest genjutsu but we never see him fight. I can't decide
Shisui was noted to be one of the most talented members of his battle-excelling clan. He had earned the nickname of "Shisui of the Body Flicker", possibly implying that he had great mastery of the Body Flicker Technique. He was hailed as one of the most powerful genjutsu users of the Uchiha clan.[3] Another testament to his prowess is that Kabuto Yakushi wanted to revive him for the war but failed to find sufficient DNA samples.
Sharingan Edit
Like many members of his clan, Shisui was a wielder of the Sharingan. He was praised alongside Itachi for having the greatest mastery of and sheer power in its usage.
Mangekyō Sharingan Edit
Shisui's Mangekyō Sharingan.
Shisui possessed the Mangekyō Sharingan which granted him access to powerful genjutsu techniques, the strongest of which was a unique genjutsu of the highest calibre: Kotoamatsukami. This technique allowed him to enter the opponents mind and manipulate them by giving them false experiences, making it seem as if they were doing things on their own free will; the victim wouldn't even notice they were being manipulated. This ability was apparently so unique and powerful, that Madara Uchiha himself (despite having access to both the Eternal Mangekyō Sharingan and the Rinnegan) coveted it, and was angry that Danzō managed to destroy the eye that was transplanted into him from Shisui at the moment of his death; Kabuto was extremely thrilled when he learned that the remaining eye is within Itachi's crow. This genjutsu however, could only be used once a decade, unless the user had Hashirama Senju's cells to augment the process, which would drastically reduce the time required