Villainous military leader Medina
Medina (Sarah Snook) was a hidden villainess--only known by her surname--from "Men Against Fire", episode 3.05 of Black Mirror (airdate October 21, 2016). She was a military leader who oversaw the military force of protagonist Koinage--mostly referred to by his nickname Stripe. Their mission consisted of exterminating "roaches", ravenous mutated humans. Medina was shown to be a rigid, yet approachable, leader of her squad.
Medina's first onscreen mission with her squad was to investigate an invasion at a Danish village that had a food store broken into by roaches. The squad learned that the villagers believed the roaches were being housed by Parn Heidekker, an outcast religious fanatic who sympathized with roaches. The squad went to Heidekker's house and, while her charges searched the home, Medina sat down with the man to talk.
During their conversation, Medina maintained a relaxed demeanor and expressed understanding in Heidekker's compassion for the roaches, but stated that they couldn't be viewed as human and that saving them would ultimately result in the destruction of humanity. When Medina's soldiers discovered roaches in a hidden room of the home, Heidekker attacked Medina with a knife, but he was ultimately defeated and arrested and Medina ordered his home be burned down, but prevented soldier Raiman from killing Heidekker. Later on, when Stripe began to experience headaches, Medina sent him to be looked at by the army doctor, Arquette.
Medina was later shot and killed by a roach sniper while her squad was investigating another roach sighting at an abandoned housing complex, with her posthumous villainous reveal coming later on. The monsterous "roaches" were in actuality perfectly healthy and non-violent humans who had been deemed "inpure enemies" by the military. To ensure that their soldiers would be able to kill their enemies without remorse or hesitation, the military implanted them with an augumented reality device known as MASS to make them view the enemies as humanoid monsters. After manipulating each military member into consenting to having MASS implanted, they would then have their memory of having the implantment done to cover their tracks, essentially turning Medina and her fellow military members into brainwashed murderers.