Hades and Sukuna

Both are the final villains of their respective series. They are immensely powerful malevolent beings who use the body of one of the main characters as a vessel to manifest their power and soul.

Their personalities are defined by sadism and overwhelming pride, and they are constantly feared and revered by other villains: Hades by his army of Specters and the lesser gods who swear loyalty to him, and Sukuna by Curses and Jujutsu Sorcerers alike.

Both bear the title of "King": Hades is the King (or Emperor, in some adaptations) of the Underworld, while Sukuna is the King of Curses. The difference is that Sukuna's title is purely honorific, whereas Hades' title is both divine and political.

Another similarity is that both Hades and Sukuna compare human beings to insects, even though Sukuna himself was originally human, and Hades himself uses a human as his vessel in order to incarnate on Earth.

Yoma of Mephistopheles and Kenjaku

Both are extraordinarily intelligent, serving as the true masterminds behind their respective stories. They have lived for centuries by assuming different bodies and identities throughout the ages. They meticulously manipulate the majority of the events, treating people as mere pieces on a chessboard, all in pursuit of achieving their ultimate goals, doing whatever is necessary to fulfill their ambitions.

They are revealed late in the story to be the fathers of the protagonists, whose sons' bodies are used to revive long-dead individuals. Kenjaku sealed one of Sukuna's fingers inside the newborn Yuji so that he would become the vessel for the soul of the King of Curses, while Yoma captured the soul of the legendary Pegasus Saint—the god-slayer of the Mythological Age—and implanted it into Tenma's body shortly after his birth.

They enjoy joking even in the most serious situations. While many villains remain stern and intimidating, they smile, taunt their enemies, and appear to genuinely enjoy the chaos surrounding them.

They also manipulate and deceive even their own "allies." Kenjaku gathered the Special Grade Curses by promising that their battle against the Jujutsu Sorcerers would create a world ruled by Curses, while allowing Mahito to believe he was acting of his own free will, when in reality all of them were merely parts of Kenjaku's grand experiment. Likewise, Yoma joined the army of the 108 Specters, swearing loyalty to Pandora and Hades while concealing his true identity as an exiled god and hiding his real ambitions. He was also responsible for manipulating Hades' soul and sealing it within the infant Alone, as well as toying with Pandora's fate itself. In conclusion, neither of them was ever truly loyal to anyone—they merely used their allies as actors in the grand spectacle they orchestrated.