The Vasa comes to mind. https://en.m.wikipedia.org/wiki/Vasa_(ship)

USSRs space shuttle, although technically that didnt fail on its own.
https://en.m.wikipedia.org/wiki/Buran_(spacecraft)

The failed Chinese attempts to use stolen SpaceX plans that resulted in at least one town that we know of being destroyed with toxic smoke and fire.

Virgin’s space program.

Boeing’s space program. Increasingly, the 737-MAX too.

Amazon’s space program.

Musk and the stupid decisions made around Starship, that resulted in over a year of setbacks since the launchpad had a woefully inadequate flame trench that everyone called out long before the first two failed launches.

The Titanic.

Related to the last one: OceanGate and the Titan.

When the Athenians starts the Peloponnesian War by invading a different city state than Sparta(to ostensibly use that city’s military against Sparta), but screwed it up, creating the conditions for them to lose said war.