Which Star Trek film features the Klingon moon Praxis exploding?

Star Trek VI: The Undiscovered Country features the explosion of the Klingon moon Praxis.

Praxis is a major Klingon energy-production facility. Its destruction creates a catastrophic environmental and economic crisis for the Klingon Empire, leaving the empire unable to maintain its previous military posture. The disaster becomes the pressure behind peace negotiations with the Federation.

The 1991 film uses the Praxis crisis as an allegory for the end of the Cold War. Chancellor Gorkon seeks a diplomatic settlement, but conspirators from both Klingon and Federation circles attempt to preserve the old conflict. Captain Kirk initially distrusts the Klingons because of their role in the death of his son, David.

The explosion is shown near the opening of the film and sets its political plot in motion. The film's title refers to the possibility of a historic peace between long-standing rivals.