Complete Monster/RWBY

*RWBY* has some especially evil villains:

* Cinder Fall is the mysterious villain of the first three volumes. A young woman who wishes to be strong, feared and powerful, Cinder recruited two young fighters named Mercury and Emerald and attacked Amber, the Fall Maiden. Defeating her, Cinder drained half her powers, leaving Amber in a coma. She then recruits the terrorist group the White Fang by massacring some of their members and forcing the rest into service. In the Vytal tournament, Cinder arranges a match between Pyrrha, who has magnetic powers, and Penny, a robot, and has Emerald use her illusion powers to make Pyrrha panic and rip Penny into pieces. Cinder then hijacks the sound system to sow discord and fear among the people and has the White Fang attack while also unleashing the monstrous creatures known as Grimm on the civilians. Merrily commenting how "beautiful" the carnage is, she has Mercury film it while gloating. Cinder then murders Amber to get the rest of her powers and in a fight with Pyrrha, cripples and then coldly executes the young warrior by using an arrow that burns her from the inside. Injured by Ruby's White Eye powers, Cinder recovers in volume five where she coerces Raven and her tribe to join Salem, later sadistically mocking Jaune over Pyrrha's murder, impaling Weiss in front of Jaune to put another death on his conscience, and killing Raven's apprentice Vernal to take her Spring Maiden powers for herself. Cruel and ambitious, Cinder left the kingdoms and alliances of Remnant shattered in her quest for power.
* Adam Taurus is spite and cruelty incarnate. A high-ranking member of the Faunus liberation group the White Fang, Adam begins verging into extremist terrorist attacks with no care for innocents who die, prompting his Love Interest Blake Belladonna to flee the group. Adam later assists in the aforementioned attack on Beacon Academy, during the Vytal Festival, unleashing Grimm on the city. When encountering Blake, Adam vows to kill everything she loves, maiming Yang when she tries to defend Blake and trying to murder Blake herself. When the high leader of the White Fang, Sienna Khan, objects to what Adam has done, Adam murders her and takes her place before ordering Blake's family killed to "keep his promise" to her. Adam then leads a White Fang attack to destroy the city of Haven, spitefully attempting to detonate explosives to kill himself, Blake and all the Faunus present, White Fang or innocent, when he's cornered by the authorities. Adam later savagely slaughters his own former followers of the White Fang when they question him and returns to stalking Blake, hellbent on murdering her and making her suffer for "ruining his life".
* Doctor Arthur Watts is the highest ranked member of Salem's inner circle, assisting Cinder in her actions in Vale to throw the city into chaos and facilitate a Grimm invasion. Once a former Atlas scientist, Watts was furious that Ironwood would acknowledge Pietro Polendina's genius over his, leading to him faking his death and eventually joining up with Salem. Returning to Atlas and Mantle, Watts schemes to have the vicious Tyrian Callows murder the supporters of Robyn Hill and frame Penny Polendina for the killings, shutting down Mantle's heating grid to allow countless citizens to freeze to death to rely on chaos and negative emotions to bring about a Grimm invasion of slaughter to further Salem's schemes.
* Unlike in the web series, Roman Torchwick in *The Official Manga* lacks his show counterpart's redeeming qualities such as his friendship with Neopolitan, who he is willing to threaten at gunpoint when she hesitates. A destructive sociopath and one of the most infamous criminals in Vale, Roman teams up with Cinder Fall and executes her schemes, organizing an attack on the city of Vale and planning to blow up a large section of the city's downtown area. At one point, Roman has Ruby Rose tied up, intending to have the White Fang torture her to death, and gleefully reveals that the purpose of the attack on Vale was to cause a Grimm invasion, which would destroy not just the city but the entire kingdom.
* *RWBY: Grimm Eclipse*: Dr. Merlot is a Grimm-obsessed scientist who founds Merlot Industries to conduct experiments on them, seeking to attract more when he ran out of subjects and having the Grimm attracted to a nearby city to work around his problem, resulting in the population being overrun and slaughtered. Moving to a remote island, Merlot creates a stronger version of the Grimm, which he releases into nearby areas where they may attack and kill as they please. Attempting to kill off Team RWBY when they come to investigate his island, when they defeat his ultimate creation, a spiteful Merlot sets his laboratory to self-destruct with all of them inside.