Warning! Contains major spoilers for Chainsaw Man!
The death of Itachi Uchiha is a pivotal and utterly tragic moment in Chainsaw Man features two deaths that are each more groundbreaking than Itachi's while revealing the true extent of the manipulative genius of the series' antagonist.
The suffering of both Uchihas is so profound because it all stems from the love an older brother has for his younger sibling. Essentially, Itachi gets caught in the middle of a longstanding feud between his clan and the village in which they reside, Village Hidden in the Leaves. Aware of an Uchiha uprising, a village leader confronts Itachi and provides him with a terrifying ultimatum: Either he does nothing and the village massacres his entire clan itself or Itachi can kill his own people but save Sasuke.
Itachi's love for his younger brother is so emphatic that he actually carries out the horrendous task himself. Feeling as though the only way to atone for his sins is to die by the hands of his younger brother, Itachi takes on the guise of a villain so Sasuke would grow up wanting nothing more than to avenge his family by murdering his older brother. Right before Itachi dies by Sasuke's hands late in the story, Itachi proves his love for him by performing the same heartfelt poke on Sasuke's forehead that he would do when they were growing up.
The tragedy of Chainsaw Man's Denji begins when he falls for the mysterious yet powerful Makima after she saves him from a life of destitution and hunger by recruiting him to be a Devil Hunter. This, combined with her natural beauty, causes Denji to become utterly obsessed with her and willing to perform any task she asks of him. Of course, Makima's actions indicate that she might reciprocate those feelings.
Later, Denji ostensibly meets a girl named Reze by accident, and they fall in love (though Denji tries to fight his urges due to his loyalty to Makima). Although Reze later reveals it was all a ruse to kill him, Denji still confesses his feelings for her, and she actually attempts to connect with him. But before she can, Makima murders her, possibly out of jealousy. Much later, a friend whom Denji initially hated but becomes quite close to is then murdered right in front of him by Makima in chapter 82. What's worse, Makima even manipulates Denji into helping kill his friend, on his birthday no less. It's soon discovered that Makima never cared for Denji and was only obsessed with the Chainsaw Man inside of him. When she failed to separate her beloved Chainsaw Man from Denji, she endeavored to ensure Denji would never be happy and live a normal life.
While Itachi's death in Naruto is tragic and incredibly ironic, his actions aren't as pure as readers believe, which is the only reason why it was so heartbreaking to begin with. Itachi may have loved his brother, but he still acted selfishly and inadvertently ruined Sasuke's life in the process. Meanwhile, Chainsaw Man's Denji is manipulated to an incredible degree by a woman he truly loved while she made him believe she cared for him but didn't. Makima had been the answer to all of his dreams when he lived in squalor, and she apparently rescued him. But it was all a devastating lie. Denji's tragedy is very much real while Itachi Uchiha's is based on the pureness of his intentions, which isn't the case at all.
