Jackson Whittemore transforms into the kanima.
Kanimas are a unique breed of shape-shifter featured in the MTV horror series Teen Wolf. Kanimas are distinguished from other shape-shifter by the fact that they take on the form of a creature that mirrors the personality of the individual. In cryptozoology, they are based on the myth of South American werejaguars. Each type of shape-shifter requires different needs. Whereas werewolves seek out a pack, a kanima seeks a master. When an individual asssumes the form of a kanima, they are no longer in control of their conscience mind and must do the bidding of whomever controls it. Upon death, a kanima may evolve into a higher life form, becoming larger, more predatory and even grow wings. (TW: Master Plan)
One known kanima is Beacon Hills High School student Jackson Whittemore. Jackson had asked to borrow a digital camera from a fellow high school student named Matt so that he could record his transformation. Matt encountered Jackson in his kanima form soon after and bonded with it. Matt was a troubled teen to say the least, and decided to use the kanima as his instrument of vengeance against those who had wronged him in the past; specifically - the members of the Beacon Hills High School swim team of 2006 and it's coach, Mister Lahey. (TW: Fury)
The kanima was responsible for several deaths in Beacon Hills in 2011 including that of Isaac Lahey's father, one of Gerard Argent's hunters named Bennet, and a mechanic - all were in some way responsible for Matt nearly drowning to death in 2006. The kanima attacked Derek Hale and Stiles Stilinsky, who sought refuge inside of a swimming pool. The kanima appeared to be afraid of water and ceased it's attack. The kanima's fear was actually a projection of Matt's own phobia of water. After satisfying his need for revenge, Matt then used the kanima to hunt down anyone who stood in the way of his goals, which at this point, involved winning the love of fellow student Allison Argent.
Jackson Whittemore later transformed into the kanima and attacked several people at a gay night club, including his close friend Danny Mahealani.
Scott McCall and Stiles identified Jackson as the kanima after the night club incident and succeeded in capturing him. They kept him housed inside of a police wagon, but Jackson later escaped. (TW: Venomous)
Jackson again transformed into the kanima at a social function hosted by Lydia Martin (ironically attended by many of the surviving partiers from the night club). He did not cause any harm to anyone, but was seen in the presence of Matt. Scott and Stiles now realized that it was Matt who was controlling the kanima. (TW: Party Guessed)
Matt knew that Scott and Stiles were searching for ways to defeat the kanima. Jackson and he tracked them down to the Beacon County Sheriff's Office where Matt had the kanima slaughter several officers, including night officer Bungalon. Derek Hale arrived to fight the kanima, but Jackson used his poisoned claws to temporarily paralyze him as well as Stiles Stilinsky.
Gerard Argent proved to be the one responsible for ultimately stopping Matt. He pulled him out to a lake where he drowned him, thus breaking Matt's control over the kanima. Gerard then became the kanima's new master. (TW: Fury)
The kanima attacks Allison Argent.
Gerard's master plan was to use the kanima to get to werewolf Derek Hale. Gerard had turned Jackson loose at the Beacon Hills High School championship lacrosse game, hoping that doing so would draw Derek out of hiding. Jackson managed to exert enough self control over himself however that he took his own life by plunging his claws into his stomach. (TW: Battlefield) Jackson died, but was reborn when a cocoon of viscous fluid formed around his body. Gerard was still in control of the kanima however and brought him to the old abandoned Hale house where the creature had his final showdown with Derek, Scott, Isaac, Erica and Boyd. Scott managed to break Gerard's hold over the kanima through trickery, having previously tainted the old man's cancer medication. Without a master, the kanima became an even greater threat - particularly when it began to evolve. It was Lydia Martin who ultimately saved Jackson, professing her love for him, enabling Jackson's subconscious mind to take control. Having pushed past his own personal baggage, Jackson was able to shed the kanima infection from his body. He then evolved into his original intended form, which was that of a werewolf. (TW: Master Plan)