In Star Trek, there's always someone out there who is bigger, faster, stealthier, and has more firepower. Ulimately, some of these opponents were just misunderstood, and simply wanted to communicate. Some of these spacefaring vessels were only threats once they fell into the wrong hands. However, in the end, we're often dealing with imminent danger that will tip the balance of power on a planetary scale or greater. What are the biggest threats out there on the final frontier?