Jujutsu Kaisen
Both are modern dark battle shounen with cursed/devil-like enemies, brutal fights, and young characters pulled into violent supernatural organizations. Jujutsu Kaisen is cleaner structurally, while Chainsaw Man is more chaotic and cynical, but the urban horror-action overlap is huge.
Dorohedoro
Dorohedoro matches Chainsaw Man's grimy weirdness: grotesque bodies, violent comedy, bizarre powers, and a cast that feels morally cracked rather than heroic. Fans who liked Chainsaw Man's unhinged tone usually understand Dorohedoro immediately.
Devilman: Crybaby
Both use demonic transformation, sexuality, gore, and apocalyptic dread to tell a story that feels emotionally raw. Devilman is shorter and more tragic, but the sense that humanity and monstrosity are collapsing into each other is very Chainsaw Man.
Tokyo Ghoul
Both follow a young man who becomes part-monster and gets dragged into a violent hidden world. Tokyo Ghoul is more brooding and tragic, while Chainsaw Man is more absurd and abrasive, but the body-horror identity crisis is the clear shared element.
Parasyte
Parasyte is a common rec because it also pairs body horror with philosophical questions about what separates humans from monsters. It is more restrained than Chainsaw Man, but fans of transformation, gore, and uneasy coexistence with a non-human power usually enjoy it.