Gerard Argent

Gerard Argent is the main antagonist of the second season of Teen Wolf and head of the Argent family, which leads werewolf hunt. Even though the ultimate leader of the hunters is the female of the Argent family, they still answer to Gerard making him the de facto leader of the hunters.

Backstory
Not much is know about his past, but it's implied he brainwashed his daughter Kate and daughter in-law  Victoria into raciest werewolf hunters and so they do what he say's, giving him total control over the hunters decisons. It's implied he ordered Kate to seduce the under age Derek Hale and murder his family.

Shortly before he is introduced, he learns he has cancer and comes up with a plan to deal with it.

Reign in Beacon Hills
He shows up for his daughter's funreal, and that night on a hunting trip, the hunter capture an innocent omega werewolf. Gerard simply cuts it in half with a silver sword. He declares that the hunters will no longer follow the code, that they will find and kill all werewolves in Beacon Hills, irregardless of their innocence.

His family have the school principle resign so Gerard takes his place, so he can keep a close eye on Allison. When Gerard meets Scott, he invites him to dinner, presenting himself as a simple kindly old man. During dinner breaks, Scott looks for a beastdiary, a book that describes any at all monsters the hunters have encountred. After Scott leaves, Gerard corners him at the hospital and stabs him in the stomach, threatening to kill his mother unless Scott did him a favor.

Later it is learned that the new monster loose in Beacon Hills is a Kanima, a monster that answers to a human master to carry out his or her vengance. It is also learned that the Kanima is Jackson, and aquiantence of Scott's. Scott and his friends top priority is find the Kanima master, while the hunters track down both the Kanima and Derek Hale's new pack. Scott was under Gerard's order to act as a mole for Derek's pack. Soon Scott is attacked by Victoria Argent and is saved by Derek, who bites Victoria. Gerard finds out Victoria was bitten and forces his son to kill her.

Allison is saddened by her mothers death, and Gerard forges a letter blaming Derek, and manipulates her minds and emotions so she becomes just like her mother and aunt - a ruthless werewolf hunter. Later the Kanima master is revealed to be Matt. When Matt and the Kanima hold Scott, his mother Melissa, Stiles, Sherriff Stilinski, and Derek hostage. They escape after the hunters arrive, but Gerard chases down Matt and drowns him, becoming the new Kanima master.

Weeks after that, Gerard has Allison call on a search for Derek's pack members, Boyd and Erica. He tells Scott that he still has somthing for him to do and threatens his mother again. At the lacross game, while the hunters are looking for the pack, Scott is told by Gerard that he will have Jackson publiclly kill someone as the Kanima at the last thirty seconds of the game unless he brings him to Derek. During a break at the game, Gerard and several hunters corner Issac, another pack member, and attempt to kill him in the locker room. Scott rescues Issac but Gerard flees. At the last minute of the game, Gerard has Jackson impale himself with his claws and in the panic, he abducts Stiles. When Gerard heads home, he finds Allison was succesful in abducting Boyd and Erica whom he tortures. Stiles tries standing up to Gerard, but is beaten horribly and let go as a message to Scott.

When Chris eventually realizes Gerard is the true enemy, he lets Erica and Boyd flee and meets up with Scott and Issac. It is learned that Jackson is still technically alive, but will become a more advanced Kanima. They take Jackson to a warehouse, where they meet up with Derek and his ressurected uncle Peter. Gerard and Allison corner them and the Kanima awakes and overpowers everyone. Allison attempts to kill Derek but is taken hostage by the Kanima. It is then that Allison, Chris and everyone else learns the truth, Gerard has cancer and has a plan to be bitten by Derek, become a werewolf himself to cure it, and kill Derek to become the Alpha. Gerard has Scott open the paralyzed Derek's mouth and declares "When it comes to survival, I would kill my own son." As Derek bites him, Gerard seemingly wins under his body violently rejects the bite. It is revealed that Scott was aware of the plan, so he and his supernaturally aware boss, Dr. Deaton mixed a supernatural repelent called mountin ash into Gerard's pills. As Gerard collapses to the ground he orders the Kanima to kill them all. Soon the Kanima is defeated by Jackson's love for his ex girlfriend Lydia, who reaches out to him. The kanima is struck down, and Jackson becomes a werewolf instead. It is later discovered the seemingly dead Gerard fled, but is currently being hunted, leaving his fate unknown.