What methods are used to destroy planets in popular movies?

[SciFiWriterGuy]

And hey, how about Wrath of Kahn's idea for a space probe that can make new life on a planet (or apparently even if fired off into a void) . . . but removes any existing life it finds?

Instant ecocide. Hasn't that idea been lofted in scifi before? A pseudo-berserker terraforming probe?

 

[Noisy Rhysling]

Did the planet in "Wrath of Cohen" actually have an ecology before the dohickey went off?

 

[UsableThought]

Did the planet in "Wrath of Cohen" actually have an ecology before the dohickey went off?

The device was intended to be detonated on a barren planet; but apparently in actual use, "no planet required." We see it blow up the Reliant, and then, as the Enterprise speeds away, we see what look like gigantic concentric smoke rings materializing one after the other, spreading outward from the epicenter of the explosion. The climactic battle takes place inside a nebula, and the Wikipedia article on the movie asserts that the device "reorganized the nebula." There is the slight problem that a sun doesn't appear to have been created for the wonderful new planet & its lush jungle life to maintain an orbit around; but eh, well, you know, science fiction.

Anyway, you can see the fireworks in this clip, see from about 0:45 to about 1:35: