The explosion expelled the toxins from his body, so he emits a signal to the other parasites to regroup. Gotou struggles to revive himself, while Shinichi begins to cry and apologize, as he eventually decides to kill Gotou and finally destroys Gotou, the other parasites and their host body.

How does Shinichi kill gotou?

He strikes the cleaver (or knife whatever it is) against Gotou's neck but he wakes up just as Shinichi plunges the knife into his neck . Not that a small knife would really kill him, but it'd do some damage at least.

Did Shinichi die at the end of Parasyte?

The parasite eventually finds Shinichi's home and then supposedly kills him, stabbing him through the heart. Migi then attempts to save Shinichi's life giving him incredible strength, physically and mentally.