Spoiler: the bug bites it.
For a story with such a sensational beginning, Kafka's Metamorphosis ends with a relative whimper (just like the world, according to T.S. Eliot). After all the hijinks, you'd expect Gregor to die in a more theatrical way. A death match between himself and his father? Or a knife attack by Grete, who goes berserk after so many weeks and months of care-taking? Or a struggle to the death with the cleaning woman, who is armed with a really, really big dustpan?
Nope. Instead, Gregor, weakened by a long period of self-starvation, collapses on the floor. The narrator notes that Gregor dies a little after 3 a.m., as if that were significant somehow.
While Kafka himself expressed disappointment with the story's ending, it actually works because of its dramatic understatement. Fittingly, Gregor slides away from the stage without attracting attention, just as the other Samsas come into their own as working, thriving human beings.
It's not even clear how his bug-corpse is finally disposed of. Reduced to a paper-thin wafer of a thing, Gregor literally disappears on the page. This finishes the reversal that began the story, where, before his transformation, Gregor was the primary breadwinner of the family and the other family members were relatively powerless—his father an invalid, his mother asthmatic, and his sister a young, frivolous girl. Now all the Samsas have jobs, the father's physically vigorous again, and Grete has matured into a marriageable young woman. The story even continues after Gregor's death, with his family taking a nice little jaunt into the countryside.
With Gregor gone, the ordinary course of things has been restored in all of its banality, which might actually be more terrifying in its absolute boringness than the Gregor's vermin form.