Kenjaku is one of the main villains in Jujutsu Kaisen series and fans have seen quite a bit of him over the years. It's worth almost every major chaotic event that takes place in the series. Born millennia ago, Kenjaku has a very special cursed technique that allows him to switch bodies. He's taken control of many bodies over the years, and while they're all special in their own way, some hold more importance than others, all while maintaining vast amounts of power.
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Unknown wizard
Kenjaku has had many bodies over the years and some of them are definitely unknown. Since he's a wizard who's lived since the Heian era and possibly earlier, we know for sure that he's had at least a dozen bodies.
We saw one among the unknown Kenjaku bodies about 400 years ago when Kashimo invited to the Culling Game. Around this time, Kenjaku had the body of a male wizard with a tail. The warlock's construction was quite large; but beyond that, we don't know much about them. It is not known whether he was a famous wizard or just an average individual. Hopefully we will learn something about him in the future.
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Kaori Itadori
Among the weaker Kenjaku bodies is also a very important figure — Kaori Itadori. As the name suggests, Kaori Itadori is Yuji's own mother. At some point in the story, she died and Kenjaku then took control of her body and used it to re-enter Jin's life. While Jin was aware of the fact that something was wrong, Kaori was blinded to the point of not wanting to see the truth.
Eventually, Kaori, who was inhabited by Kenjaku at the time, gave birth to Yuji. This basically ties into Yuji Itadori's story and is shocking to say the least. We also know for sure that even after Yuji's birth, Wasuke told Jin that something about Kaori was different than before. However, once again, Jin ignored every piece of advice he received. When it comes to strength, fans know that Kaori wasn't that strong. However, she had a cursed anti-gravity system technique. As the name suggests, this system allows the user to negate all gravitational forces, or at least significantly weaken them. Kenjaku gained access to this technique through her.
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Original body
Kenjaku's very first body would of course be his original. Sadly, fans never got to see this body in the story, and it's highly unlikely that we ever will, given that he's already dead at this point. In this Kenjaku body, he probably existed during the Heian era or maybe even before that.
We do not know exactly how he died and under what circumstances it happened. We also don't know how Kenjaku awakens his cursed technique and who his very first host was. All these things are still a mystery and hopefully the series writer will explain everything to the fans through bits and pieces of different information in future issues.

The creator of Jujutsu Kaisen reveals his original plans for Gojo vs Sukuna
Gojo vs Sukuna ended with Gojo's death, but Gege's original plans for the fight have now been revealed.
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Noritoshi Kamo
Among the stronger Kenjaku bodies is Noritoshi Kamo. Fans know that Noritoshi Kamo was a very infamous sorcerer who committed all sorts of atrocities in the past. He is said to be the most hideous wizard of all time. However, little do the people know that it was actually Kenjaku who was carrying out heinous acts using Noritoshi's body.
At some point he died and his body was then taken over by Kenjaku who then used his body to commit all sorts of atrocities and it was his name that was sullied. Along with this, the name of the Kamo Clan itself was tarnished. It is well known that he used this power to create images of death.
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Suguru Geto
By far the strongest body Kenjaku had used JJK it's Suguru Geto. After the events of the Night Parade of 100 Demons, Geto was defeated by Yuta Okkotsu, but was finished off by Gojo.
At the very end, Kenjaku used his cursed techniques to get to Geta's body. He wanted the power to manipulate the cursed spirit and he definitely got his hands on it. He also gained the power of all the other abilities Geto possessed, along with his memories. Eventually, Kenjaku died in this body in the Shinjuku Showdown Arc. Yuta was the one to end him for good. Basically, Kenjaku's very last body was Suguru Geto, and his plans ended prematurely when Yuta lifted his head from his shoulders.
All chapters of Jujutsu Kaisen are available to read through Manga Plus and Viz Media.