Star Trek has plenty of amazing villains. Some have understandable motives, while others are insane killers who have brought untold destruction to the galaxy. Entire planets and entire societies have been wiped out through the actions of lone madmen.
In this list, we're going to look at the worst of the worst, the villains who have managed to amass the highest kill-counts out of any characters in Trek . Everyone loves a good villain, but these monsters are unforgivable. They have killed on scales that are hard to even fathom.
We're going to focus on individuals, rather than groups here, so, while the Klingon and Romulan Empires oversaw a lot of death and destruction, they won't be considered as groups because they did not have single individuals who directed the killing. Wars will only be considered if they were conducted by one specific person.
Data's maniacal identical brother Lore was designed with faulty programming that made him extremely unstable.
When Dr. Soong was working on Lore at the Omicron Theta colony, he began displaying signs of malevolence and thoughts that he was better than Humans. This led the other colonists to distrust the android, and they demanded that he be deactivated.
To get revenge on the colonists for rejecting him (and wishing for his death), Lore lured a powerful space creature known as The Crystalline Entity to the colony, where it wiped out most of Omicron Theta's hundreds of inhabitants.
Data, Noonian Soong, and Noonian's wife Juliana all survived the initial attack, though Juliana was severely wounded and needed to have her consciousness transferred into an android body. Though, later (in the episode Brothers ), Data and Lore found Dr. Soong (who they both had thought died in the attack) and Lore killed him and stole his newly-designed emotion chip because he still believed that the doctor cared more about Data.