(covers information from several alternate timelines)
A subspace implosion is a violently destructive phenomenon that could be produced using a warp core.
In an alternate timeline in 2165, Jonathan Archer initiated a subspace implosion on board Enterprise NX-01 in order to eliminate a series of parasites with which he had been infected twelve years earlier, which inhibited his ability to form new long-term memories. He did this by initiating an overload in three of the ship's plasma injectors, causing a feedback pulse to travel through the reactor, destroying the ship. As the parasites existed in a state of interspatial flux, originating from outside normal spacetime, destroying the parasites in the present also had the effect of neutralizing them in the past, changing history in such a way as the infection never occurred. (ENT: "Twilight")