The cursed spirit Mahito from Jujutsu Kaisen shares the same twisted affinity for human experimentation as My Hero Academia's All For One and Naruto's Orochimaru.
In Naruto, the main drive behind Orochimaru's experiments has always been the pursuit of immortality through the creation of the coveted Living Corpse Reincarnation. It's a combination of this and his psychopathic tendencies that have allowed him to completely drop experiments, usually out of boredom, before he moves on to his next deplorable scheme. The most horrific of his many experiments involved infusing 60 children he kidnapped with DNA from the Leaf Village's First Hokage, Hashirama Senju, to recreate his Wood Release.
In My Hero Academia, All For One's Nomus are biologically engineered from humans to possess multiple quirks. Some of them even share the corpse's personalities. The Nomu that Endeavor battled earlier on had been so obsessed with fighting the most powerful hero because a ruffian with a similar personality had been used as the creature's base. All For One even made the League of Villains member known as Kurogiri from the corpse of Shirakumo Oboro, who died during a rescue mission.
In Jujutsu Kaisen, the cursed spirit Mahito also enjoys experimenting on humans, but it makes sense, seeing as he was born from the stomach of people who hate and fear other humans. This really twisted affinity is first presented in chapter 19 when Mahito is able to lure a young boy named Junpei after the villain distorts the bodies of three students Junpei hated.
Although it's obvious that Mahito enjoys this twisted pastime, his experiments are meant to use them in battle. One of his tactics involves shrinking humans into some sort of misshapen mass so that he can carry them around with him (sometimes in his mouth) so he can release them to attack at a moment's notice. And although he does blow up some humans into deformed flesh balloons, he reveals in chapter 21 that its only purpose is to help him see how small he can get them. Experiments aside, one of Mahito's more disturbing moments takes place in chapter 55 where he pins a man to a wall and tortures him to test whether or not his victim possesses cursed energy. This is his way to see whether these humans have any potential.
Out of all three villains, Jujutsu Kaisen's Mahito and My Hero Academia's All For One share the most similarities, as they generally conduct their experiments to create mindless soldiers who will follow their orders. This isn't to say that Naruto's Orochimaru hasn't used his lab rats in battle. The most prominent examples being some recipients of his Cursed Seal of Heaven, most especially Kimimaro and Sasuke, both of whom Orochimaru branded so he could take over their bodies after the seal corroded their minds. That said, it should be mentioned that All For One does experiment on Tomura Shigaraki with the intent of taking over his body, just like Orochimaru, an endeavor Mahito would never pursue, as his group of cursed spirits believes curses are the true representation of humans and should therefore take their place. Regardless, although these villains have different goals and methods, they all experiment on humans in some way to achieve their appalling objectives--and enjoy it immensely.