Planet destruction

Star Trek

Xindi superweapon

http://www.youtube.com/watch?v=A-q0hjSnbUA

As seen here, Xindi superweapon fired beam which penetrated planet's crust, reached its core and blew up planet from inside. Basically "Enterprise" version of Death Star - beam destroys planet despite not having DET power to do so.

General Order 24

General Order 24: An order to destroy all life on an entire planet. This order has been given by Captain Garth (Antos IV) and Captain Kirk (Eminiar VII). On neither occasion was the order actually fulfilled. (TOS: “A Taste of Armageddon”, “Whom Gods Destroy”)

Founder's sun-crushing bomb

Founder posing as Deep Space 9's Dr. Bashir attempted to destroy the sun using a bomb composed of trilithium, tekasite and protomatter. (DS9: "By Inferno's Light"). He was prevented from doing so by Defiant; it should be noted that bomb was relatively small, smaller than full-sized photon torpedoes used by capital ships.

Star Wars

Canon

Death Stars

Two battlestashions with ability to destroy planet. Effects of planetary destruction do not correspond to DET weapon, but rather to some sort of hyperspace-based or other technobabble weapon - that wiev is supported by ANH novelization.

Expanded Universe

Base Delta Zero

Star Wars version of General Order 24. Heavily inconsistent - in some cases turbolaser bolts merely 'put large patches of forrest on fire' while in others entire surface of planet was 'evenly cratered' and looked like surface of Moon after attack by single ISD. Given that turbolaser's firepower is in megatons, order is actually realistic.

HERE is a quote about a BDZ:-


"“Sir, what about bombardment? Is there a stage for that?”

“Blasting a planet from orbit is easy — you don’t need me to tell you how to do that. Limited orbital strikes would occur during the invasion stage. Just hope you are never given a Base Delta Zero order, lieutenant. Ah, yes, another question?”

“Sir, what’s the Base Delta Zero order?”
“Base Delta Zero is the Imperial code order to destroy all population centres and resources, including industry, natural resources and cities. All other Imperial codes are subject to change, as you well know, but this code is always the same to prevent any confusion when the order is given. Base Delta Zero is rarely issued. ….”
– “A World to Conquer” "


Sun Crusher

Small starship with special torpedoes used to destroy stars. Possibly influenced by Founder's sun-crushing bomb.