T'Kon
The T'Kon are an extinct super race that once lived in the Milky Way galaxy in Star Trek. Long before the birth of the Federation, the T'Kon ruled a large empire, but their civilization died away when the sun of their home system went supernova. They appear only once, in the TNG episode "The Last Outpost", represented by some kind of AI guardian that called itself a "Portal", programmed to examine petitioners trying to enter the empire's territory.
Attributes
The Portal had tractor beam technology sufficient to immobilize both a Federation Galaxy-class starship and a Ferengi starship at the same time, simultaneously draining their power sources quickly enough to cripple both ships in a matter of minutes. It also possessed telepathic abilities that allowed it to read the thoughts of humans, but it was not able to read the minds of the Ferengi.
At the height of their power, the T'Kon reportedly possessed technology capable of moving stars, but with such power at their disposal, it seems strange that their entirely civilization was destroyed by the supernova of a single star.