Q

Q is an omnipotent life form of no true definition encountered by Starfleet on numerous occasions, normally when he or his species, the Q Continuum, deemed it necessary for humanity to "learn a lesson." The Q were first encountered by the USS Enterprise-D in 2364 during the Farpoint mission, and encountered dozens of times afterwards, most significantly when the original Q threw the Enterprise into the Delta Quadrant where they made First Contact with the Borg.

In 2414, Q threw James Copper into the past to the Battle of Wolf 359, and forced him to watch a Cube annihilate 39 ships from a viewing port on the USS Saratoga. When questioned as to why he was brought here, Q told him that he merely wanted to remind humanity of the threat the Borg posed, and to show him that they had achieved what was thought to have been unthinkable; they had achieved the successful assimilation of an Undine soldier.