Werewolf

Werewolves are a race of partially-human supernatural creatures, able to morph into a combination of human and wolf during the period of a full moon, that have been encountered by hunters such as Sam and Dean Winchester. It has been stated that werewolves and skinwalkers are cousins. There is no known cure for lycanthropy.

Characteristics
Werewolves are humanoid carnivores, the ultimate combination of wolves and humans. They feed on prey found nearby, which, due to the increase of urban areas, are mostly humans. When they devour the flesh of victim they leave a recognizable trace on the prey: they always eat the heart, and although they do sometimes eat more of the body, but never leave the heart. The transformation only occurs after a werewolf bites a victim, the way werewolves continue the spread of lycanthropy

In their werewolf form, their bodies change rapidly, changing into a fitting definition of predators. Their nails increase to sharp, long claws, fangs increase in size and eyes resemble those of a wolf rather than of a human.

Types of Werewolves
There are two types of werewolves shown in the series--regular werewolves, and pureblood werewolves.

Regular Werewolves
Regular werewolves can only turn into a werewolf during nights coinciding with the peak of the lunar cycle during their sleep - as Samand Dean checked if they succeeded in stopping Madison from turning into a werewolf again by remaining in her apartment during a night under a full moon, and no werewolf transformation was seen while she was awake. However, when the next night arrived, Madison turned during her sleep and went on another feral rampage.

In the series, the people affected by the disease have a short-term memory loss, often leaving them in confusion of wounds which might have been caused during the night. In the series, Dean manages to cut Madison with a silver knife, making her wonder how was the wound created.

Despite having no control over and during their transformation, certain fragments of their personality and fears can be imbibed by the werewolf's mind, especially strong ones. Aside from hunger, suppressed fears or aggression can drive them to kill in their beast form. As such, a werewolf's attack may be controlled by these emotions, depending on which one is dominant. When Madison was attacked, she was turned into a werewolf when her attacker felt an intense drive to mate. On another hand, Madison defensively killed a stalker when she felt that the man was becoming too invasive with respect to her privacy.

Pureblood Werewolves
In pureblood werewolves, ones that are closer to the Alpha up to the fourth generation, the wolves have more control over themselves and are less feral. Their human side retains a lot of control and they remember what happened afterwards and can transform anytime they want. Purebloods can also access some of their werewolf powers, even in human form such as enhanced strength and speed.

Purebloods also can feed on just animal hearts, but if they get a taste of human hearts, it is harder to control themselves and they will be drawn to eating human hearts, and with each heart eaten the temptation escalates. It is still difficult for them to eat animal hearts even if they can resist, one stated he had to force himself to swallow them. It is unknown if purebloods belonging to the four generations mean they are offspring or are simply human beings turned by first-, second- or third-generation pureblood, or if both cases will hold true.

Powers and Abilities

 * Shapeshifting - Werewolves transform into a wolf-like creature only under a full moon. However, in season 6, All Dogs Go to Heaven, Sam tells Dean that werewolves no longer change under a full moon, but under half moons. The demon Crowley agreed with Sam by saying "werewolves changing under a full moon, so... 09." It is presumably because of the upcoming arrival of Eve. Pureblood werewolves can shape shift at will and transform anytime they want however, they somewhat lose control whenever they feed on human hearts.
 * Infectious bite - Through a bite, a werewolf can turn another person into a werewolf while in beast form.
 * Claws and Fangs - Werewolves have powerful claws and are able to cut solid walls. Their fangs can tear off and eat human flesh and can rip out a human heart right out of their chest cavity.
 * Supernatural Strength - A werewolf's strength is much greater than a human's. They can easily overpower humans and can rip flesh and bones with amazing force, their strength is notable even for monsters, able to smash stone with there bare hands. All werewolves seem to have the same or atleast a similar level of strength, as during there fight, Michael was unable to gain any actual advantage over Brian, dispite the significant difference in their physique.
 * Enhanced Agility - Their agility is greater than humans, often allowing them to perform incredible jumps and sprints easily.
 * Super speed - A werewolf can move really fast, able to move from place to place in seconds.
 * Super stamina - Werewolves don't tire easily.
 * Super Senses - All werewolves are able to see better than humans in darkness, similar to actual wolves, there sense of smell is equally enhanced.
 * Invulnerability - Werewolves can't be killed by conventional means and weapons. Silver however, can kill them.
 * Regeneration - Werewolves can regenerate all non-lethal damage, purebloods are even able to completely heal their orginal bites.

Vulnerabilities

 * Silver - A werewolf's only known weakness is their vulnerability to silver, as they can be killed with a silver knife or bullet. Contact with silver will hurt them.
 * The Colt - As the colt has the ability to kill almost anything, it is most likely a weakness to werewolves.
 * Vamptonite - Edgar states the Leviathan additive will kill wolves as well as vampires. (There Will Be Blood)
 * Severe Dismemberment - Signifcant damage can kill them, Kate is able to kill Brian Wilcox by ripping him to shreds.

Known Werewolves
There have been six werewolves that have been on the series:
 * Alpha Werewolf
 * Madison (deceased)
 * Glen(deceased)
 * Professor Ludensky (deceased)
 * Michael Wheeler (deceased)
 * Brian Wilcox (deceased)
 * Kate

Trivia

 * Have been mentioned more often than any other monster, but have only appeared twice.
 * Due to their great physical prowess, Werewolves seem to be highly respected monsters in hunter communities, as stating they've hunted them is seem as sign of achievement.
 * Madison had a visible bitemark, whereas Michael did not. It is unknown if this is because Madison's bitemark was intended for creating a mate, or because Michael was bitten by a Pureblood Werewolf. It was never clarified in the series if werewolves always have a bitemark.
 * Werewolves on supernatural are both different and similar to Werewolves in traditonal folklore. In traditonal Folklore, Werewolves are said to be humans that have the ability to transform into a wolf at will. The transformation from man to wolf is said to be complete but they appear to be much bigger and stronger than a normal wolf and would retain their human eyes in wolf form. However, Medieavl monks and Priests believed that complete shapeshifting was impossible and that it was the fruit of trick of Satan, but people that were Werewolves took on wolf like traits like fangs, claws, and dark skin, wolf eyes, and superhuman abilites just like the Werewovles on Supernatural. Werewolves were believed to possees superhuman strength, speed, agility, senses, and durablity in their wolf form and it's human intelligence would remain in their wolf form. They didn't need the fullmoon to shapeshift. They didn't black out or have no memory of their actions and could shapeshift from human to wolf at will, day or night, just like Pureblood Werewolves on Supernatural. The only big differents between Werewolves from Supernatural and the Werewolves of folklore, is that Werewolves are created by being bitten by a Werewolf and Werewolves can only be killed by silver. In tradtional folklore, lycanthropy was innate, it was either voluntary or involuntary. Volontary creation requier putting on a wolf skin, oinments, or patc with the Devil. Involuntary Werewolves were born with the condition due to a curse put on their birth, either born form a human and Werewolf parents, born as a seventh son of a seventh son, born on a new or full moons, or born on December 24th or 25th. Folklore Werewolves were kiled with ordinary weapons and methods, like guns, knives, swords, beheading, and fire. They were put on witch trials and were executed if proved that they werte a werewolf.