Xindi superweapon

The Xindi superweapon was a massive mobile particle beam weapon designed to destroy entire planets. It was built by the Xindi in the 22nd century who hoped to destroy the planet Earth to prevent the destruction of their future homeworld by Humans in the 26th century, as they had been told would happen by the Sphere Builders. 

Probe
The weapon had at least three stages in its development the first of which was a small probe piloted by a single Xindi-Reptilian, a soldier hand-picked by Commander Dolim. 

In March of 2153 the probe was launched in a test attack against Earth, bypassing Earth's defences and arriving in immediate orbit though the use of a subspace vortex. As soon as it entered orbit the probe fired, cutting a 4000 kilometer swath from Florida to Venezuela, and killing seven million people in the process.

Telemetry from the test attack was transmitted back to the Xindi Council and after the attack the pilot activated the self destruct. Debris from the probe and the corpse of the pilot (surviving thanks to an undetonated charge in the vessel's engine) landed in Central Asia, where it was recovered by a Vulcan transport and handed over to Starfleet in San Francisco for analysis - quantum dating of the wreckage suggested components came from the future, collaborating what Jonathan Archer had been told by the Suliban Cabal's temporal benefactor and pointing Starfleet towards the Xindi. In response the starship Enterprise was launched on a mission to stop the expected follow-up attacks from the Xindi. 

Second prototype
Continuing the development of the weapon the Xindi built a larger unmanned prototype which they tested, under the supervision of the weapon's designer, Degra, in the Calindra system in December of 2153. 

The test did not go as the Xindi had hoped, causing significant damage to the target moon, but not completely destroying it. This was thanks to sabotaged materials in the weapons construction by the Xindi-Arboreal, Gralik Durr, who had been convinced by Jonathan Archer of the deadly application - in the construction of the weapon - the kemocite he supplied the other Xindi. The kemocite had also had its radiolytic signature altered to allow it to be tracked by the Enterprise to the test site. 

Working with the Andorian warship Kumari the Enterprise devised a plan to steal the weapon. Following the test firing the Kumari entered the system and tractored the prototype into it's hull. The Andorians then planned to betray the Enterprise and return with the weapon to Andor, using it as a deterrent against the Vulcans. Not willing to allow this to happen Archer had T'Pol enter the activation codes to issue an overload command. The Andorians jettisoned the weapon just in time for it to not destroy their vessel as it exploded. 

Final weapon
The final version of the weapon was constructed by the Xindi-Aquatics on Azati Prime, and following Azati Prime's discovery by the Enterprise was moved to an underground facility on the Xindi Council planet for completion. 

When it became apparent some members of the Xindi council were starting to question the attack on Earth, thanks to the arguments put forth by Jonathan Archer, a force of Xindi-Reptilians and Xindi-Insectiods decided to hijack the weapon, determined to complete the attack. Despite the best efforts of the Enterprise and the forces of the rest of the Xindi, the Reptilians and Insectiods successfully escaped with the weapon into a subspace vortex. 

The weapon headed straight for Earth, but a team from the Enterprise assisted by the Xindi followed closely behind and when the weapon arrived they transported inside to destroy it from within by causing an overload. 

Legacy
Following the successful completion of the mission to stop the weapon the Enterprise and her crew received a heroes welcome at their return to Earth. However the incident also provoked heightened levels of Xenophobia on Earth, resulting in gathering support for the Terra Prime movement in 2155. 

Also in 2154 the Vulcan Administrator V'Las showed the Vulcan High Command footage of the second prototype of the weapon, claiming the Andorians were adapting the Xindi technology to use against the Vulcans, hoping to provoke a conflict between Vulcan and Andor. 

In 2370 a reconstruction or replica of the probe prototype was in possession of a Starfleet conspiracy who stored it in a secret facility on, or near, Earth. 

In an alternate 2374, USS Voyager (NCC-74656) chief engineer B'Elanna Torres commented that the strong-force reversal field emitted by the Species 8472 bioships to destroy planets was similar to the pulse emitted by the Xindi superweapon.