- "Lonelyhearts": Billy Capra is an especially dangerous Ziegevolk, responsible for committing numerous rapes across the country. Ziegevolk naturally produce powerful pheromones that make themselves come across as more attractive and charming, especially towards the opposite sex. However, through consuming a special type of toad, Billy vastly enhances his powers, granting himself a form of Mind Control. His MO is to find vulnerable women in the nearby bar, then use his pheromones to force them to come to his bed and breakfast. Once there he imprisons them in cages in his basement, pumping the room with a powerful sedative gas to keep them docile, then rapes them over and over again until he gets bored with them. Having already kidnapped three women in Portland for a period of several months, Billy tries to capture Faith Collins but she manages to escape. Tracking Faith down, Billy suffocates her—despite his race's long standing nature of nonviolence—to keep his crimes secret. A few nights later, he tries again with another woman, Lisa. Realizing the police are onto him Billy attempts to abandon Portland, forcing Lisa to go with him.
- "Game Ogre": Oleg Stark is an especially violent, hot-tempered Siegbarste, or ogre. A hitman for hire, Stark was arrested for a series of brutal murders, and escapes jail years later, beating his guards into a coma before seeking revenge. Stark hunts down and kills the prosecuting lawyer, cutting out her tongue first; cuts off the hand of the jury foreman before beating the man to death; and then goes after the judge, beating the man senseless before shoving his gavel down his throat. Stark tries to draw out Hank Griffin, the detective who arrested him, by setting off an explosion in a public area near his apartment. When this fails, Stark murders an old man for his car and hospitalizes Nick in an attempt to get his location. He also attacks Juliette simply for interrupting them. Brutal and cruel, even by the standards of the occasionally monstrous Wesen, Stark was an utter beast.
- "Organ Grinder": Dr. Levine is the head doctor at a free clinic, known as the Folter Clinic. She is also the head of a ring of Geiers who harvest human organs in order to create products for Wesen. A vulture-like race, Geiers are infamous for this disturbing practice, but traditionally they only targeted the dead or dying, befitting vultures' status as scavengers. Levine, however, takes this brutality a step further, luring in or kidnapping homeless teenagers, then vivisecting and eventually murdering them. Openly taking pleasure from her grizzly acts, she forces a boy named Hanson to watch as she prepares to cut open his sister, and barely reacts as her subordinates are gunned down by Portland Police, when they rescue the teens. Having murdered countless people, all in the name of profit, Levine established herself as one of the most disturbed killers amongst a race of them.
- "Last Grimm Standing": Leo Taymor is a corrupt probation officer, and the leader of a gang of Löwen who resurrected the Löwen Games in Portland. While modern day Löwen have long abandoned the games, seeing them as a dark chapter of their history, Leo happily runs them for money. Using his position in overseeing parolees to find victims for his goons to kidnap, Leo then forces the captured Wesen to fight to death, preparing the combatants via Electric Torture and feeding them the bodies of the dead participants before each fight. Desiring more money, Leo broke his agreement with Sean Renard, and started kidnapping other Wesen to make the fights more interesting. Reducing the Skalenzahne, Dmitri Skontos, to nothing more than a feral beast, and caused the deaths of an elderly couple when Dmitri managed to escape. Kidnapping Dmitri's friend, the Dickfellig Brian Cooney, Leo forced him against Dmitri, and when he lost, Leo had Dmitri kill him. Knowing a Blutbad would be a big draw, Leo had Monroe kidnapped and almost killed before Nick interrupted the fight. To save his friend, Nick himself was forced into the arena. A heartless beast driven only by greed Leo abandoned his fellow Löwen when the Portland Police raided the games, and tried to grab all his blood money, before dying at the hands of Renard's assassin.
- "Bad Teeth" & "The Kiss": Marnassier is a Mauvais Dentes, a rare Saber-Tooth Tiger-like creature, and a vicious international assassin with a taste for human flesh. Responsible for at least twelve murders across Europe, he's employed by the season's Big Bad, Prince Eric Renard, to kill Nick Burkhardt and steal his key. Smuggled into Portland in a shipping container, Marnassier ensured that there were others in there with him. During the journey he slowly ate them, even leaving a taunting message written in his victim's blood, discussing how much enjoyed the taste of their flesh. Arriving in Portland, Marnassier ambushed a security guard and two harbor cops who investigated the blood seeping out the container and found his victims' lacerated remains, flaying all three of them men alive then spent an hour eating parts of their corpses. To lure Nick into his trap, he tricked FBI Agents Durwell and Kanigher to come to him. Marnassier taunted them by ripping a chunk out of Durwells neck right front of his partner, before overpowering both agents, killing Durwell. He then forced Kanigher to call Nick to come him alone, threatening to kill her if he refused; he immediately mutilated and killed Kanigher the moment he hung up.
- "The Waking Dead", "Goodnight, Sweet Grimm"; season 3's premiere "The Ungrateful Dead": Baron Samedi, The Dragon to Prince Eric Renard, is a particularly dangerous Cracher-Mortel, a pufferfish-like creature whose venom reduces people to a zombie-like state. Hiding behind a front of charm and culture, Samedi is a cold-blooded sociopath content to destroy a city in pursuit of his goals. Arriving in Portland, he begins infecting innocent people, leaving them aggressive, feral and unable to disobey his orders. Taking his nearly-hundred victims, he imprisons them in shipping facilities his efforts causing several violent disturbances and deaths. Knowing his poison is unimaginably painful, Samedi takes obvious pleasure outof infecting others, laughing to himself as his victims wriggle in pain. Releasing dozens of his infected slaves, he sends them into the heart of Portland, where they tear the place apart and attack everyone they encounter. Luring the heroes into the storage yard, he releases all his remaining captives to rip them apart. Personally taking on Nick, he lures him into a locker then infects him, as capturing Nick was Eric's plan and Samedi's only intention all along. Thus he leaves, completely uncaring of the damage his victims will cause without him to control them or that they will all die when the poison reaches its final stage.
- Jack the Ripper himself is the hidden secondary villain of the season. Infamous for murdering and mutilating numerous women in Whitechapel, Jack actually began his reign of terror almost a hundred years earlier. In 1789 Paris, he murdered several Wesen women so brutally that, despite not being Wesen, a local Grimm killed him. A spiritual being, Jack has been possessing innocent people for centuries, using them to carry on his killing spree—with the heavy implication that all Jack the Ripper copycats were him-until they die, when he stays dormant until he can find a new host. Latching onto the resurrected Sean Renard, he arrives in Portland. Throughout the season he tortures the later through horrific hallucinations, forcing him to relive his shooting and physical pain, almost driving him mad. Growing strong enough, Jack takes over Renard, and uses him to murder a Wesen prostitute in his standard manner. He kills her friend for helping the police, and then murders Henrietta for trying to help Sean. Impersonating Renard, Jack kidnaps Wu, bringing him along so he can watch helplessly as Jack kills his next victim, likely intending to kill Wu afterwards. When the heroes try to trick Jack into thinking his host is dying so he'll leave him, Jack attempts to strangle Rosalee. Completely psychotic, solely motivated by his own sadistic entertainment and possessing a body count spanning centuries, Jack, despite being non-Wesen, stands out as one of the worst things Nick ever faced.
- Conrad Bonaparte, the Big Bad of the season and a very powerful Zauberbiest, is the co-founder and leader of the terrorist organization Black Claw, which consider Wesen the Master Race and aim to conquer the world. Responsible for many of Black Claw's attacks around the world, Bonaparte organizes their attempts to subjugate Portland, setting up local political candidate Andrew Dixon then assassinating him so Sean Renard could take his place. Black Claw spread destruction and murder throughout the city, including inspiring the temporary resurrection of a barbaric Human Sacrifice ritual, and launching an attack upon Wesen-run businesses that didn't join them. Arriving to personally oversee events, Conrad sent loyal agents to die to provide a distraction; forced Adalind Schade to join them by threatening her children; was both directly and indirectly responsible for many deaths, including Monroe's Uncle Felix; destroyed the local Hadrian's Wall base; and painfully cursed Adalind for being uncooperative. Using his powers, Conrad slowly, agonizingly murdered Meisner, taking obvious pleasure as he did so; and tortured Nick Burkhardt by inducing both extreme physical pain and nightmarish hallucinations involving Nick's son. His attempt to secure a book detailing the lineage of all Grimms so he could control them failing, Bonaparte fatally wounded Eve, tortured Nick's address out of Adalind and ordered an all-out assault upon Nick and his allies. Following Nick destroying his entire Army, Conrad displayed no regard for his fallen followers, only acknowledging that he underestimated Nick before trying to personally murder him. Underneath a calm and seemingly-friendly exterior, Bonaparte was a man of no morals or standards, driven by an unshakable belief in Wesen supremacy and complete disregard for even his most loyal followers.
- Zerstörer—German for "Destroyer"—the Greater-Scope Villain of the entire series and Big Bad of the season, is an ancient devil-like creature who millennia ago stole a Magic Staff to bring about Hell on Earth. Defeated by the ancient Grimms, he was imprisoned in Hell, where animalistic Wesen rule and humans are "walking meat". Ruling over the chaos, Zerstörer waited until 2017 when he could escape. Needing a Grimm to break the spell, Zerstörer targeted Eve, taking control of her body to inscribe his symbols with her own blood, then stalking and almost strangling her, all so she would lure Nick into his realm. Once free, Zerstörer's first act was to skewer a man for just being in there, and then murdered another personby causing his eyes to explode—for his clothes . Seeking the Shaphant, his destined child bride—and Renard and Adalind's preteen daughter Diana—and the final piece of his staff, Zerstörer went on a murder spree, climaxing with him slaughtering every single person within the precinct, including Hank and Wu. He then targeted everyone who Nick cares about: forcing Eve to slowly stab herself to death; stabbing Renard through the heart when he tries to protect Diana; using Nick's ax to kill Adalind; turning his staff into a serpent to poison Monroe and Rosalee; and finally strangling Trubel; all to force Nick into a deal to give him the staff's final piece and thus the power to merge the world with hell, creating eternal chaos for him to rule over. Cruel, cunning, and incredibly powerful, Zerstörer was an opponent like nothing else Nick had ever encountered.