With his superior physique, heightened senses, chainsaw powers, enhanced healing, and a variety of more abilities, it seems like quite a task to defeat Chainsaw Man in the first place. In an earlier battle, it took for a coalition between the Death, War, Hunger, and Control Devils known as the Four Horsemen along with the 7 weapon devils to reduce him to a “near-death state”, but is it possible to defeat Chainsaw Man?
It is established in the series that no Devil can ever truly die since they will just be revived in Hell and Devils who die in Hell resurrect in the human world without any of their earlier memories. The only known way for a devil to be erased from existence without being able to return is by being eaten by the “Hero of Hell”, which is Chainsaw Man himself.
Hence from the information that has been revealed in the series so far, we can conclude that Chainsaw Man can never truly die since it seems quite impossible for him to be able to eat himself. However, this is restricted to the original Chainsaw Man or Pochita who is the Chainsaw Devil.
It is quite possible to kill Denji, who is the current Chainsaw Man by making him break the contract with Pochita or bring Pochita who acts as his heart out of Denji’s body. However, this would just revert to Pochita becoming the Chainsaw Man again.
This seems like a ridiculous advantage which might even bring the hype of battles down for fans since the stakes are always low for the Chainsaw Devil, however, there is still very little we know about Devils along with a mountain of information yet to be revealed and so the prospects for a way of killing Chainsaw Man being uncovered in the future are very high.