#1: Species 8472.
The winner of my scariest races in Trek is so scary, it doesn’t even have a name, just a species number given to them by the Borg upon their attempt to assimilate them, an attempt that would prove to be unsuccessful.
Species 8472 makes their first appearance in the two-part Voyager episode “Scorpion parts 1 &2”. The unnamed species is made up of biotechnology, giving them immunity to all conventional attacks, including assimilation by the Borg. Not only do Species 8472 possess an immunity to assimilation, but their bioships are far more advanced than even the Borg cubes, enabling them to destroy the cubes in seconds.
The biotech that forms the genetic makeup of Species 8472 gives them an ability to infect their victims, whereupon the alien cells will “eat the victim alive” as what nearly happened to Harry Kim in “Scorpion”.
Species 8472 is not only aggressive towards the Borg but to all other sentient life in the galaxy with no exceptions, declaring “The weak shall perish”. While I admit, Species 8472 doesn’t have quite the screen presence of the Borg, I must give them the nod over the Borg as the scariest species in the galaxy for one reason.
A species that is feared and hated by the Borg itself, a species that has no fear of the Borg and treats them with the same extreme prejudice that it shows for every other life form in the galaxy, deserves the #1 spot. To my knowledge, in the entirety of the Star Trek canon, only one species matches that criteria, and it is the species without a name—Species 8472.
These are my three most feared species in the galaxy, but I would love to hear how I got my list woefully wrong, what species I mixed up in my ranking, or what species I insulted by not including them at all.
Let me know in the comments section, and happy Halloween.