Tolian Soran was an El-Aurian scientist who spent decades trying to return to the Nexus and was willing to destroy whole star systems to do it.
Tolian Soran was an El-Aurian who lost his family when the Borg destroyed his world. In 2293 he was one of the refugees aboard the transport Lakul when it was caught in the energy ribbon of the Nexus. The Enterprise-B beamed him out, but he had felt the perfect contentment of the Nexus and became consumed with going back.
Over the following decades Soran worked out how to alter the ribbon's path by destroying stars. In 2371 he attacked the Amargosa observatory and destroyed its star with a trilithium probe, aided by the Klingon sisters Lursa and B'Etor, who wanted the weapon in return. He then planned to destroy the Veridian star, which would have killed the inhabitants of Veridian IV, so that the ribbon would sweep over him on Veridian III. Picard, joined by James T. Kirk from inside the Nexus, stopped him, and Soran died when his launcher exploded.
Soran's obsession drove the events of Star Trek Generations, bringing together Picard and Kirk and leading to the loss of the Enterprise-D.