Werewolf

Werewolves are a race of supernatural creatures that were once human, but now have the power to transform into a wolf whenever there is a full moon, that have encountered by hunters and both Sam and Dean Winchester. It has been stated that werewolves and skinwalkers are cousins, and that there is no known cure for a werewolf to turn back human.

They have seen only once as 'monsters of the week' in the series, being their appearance in 'Heart', and they have been mentioned four times in other episodes.

Characteristics
In the series, a person becomes a werewolf by being bitten by a one of them. After becoming one, they hunt down humans and they kill them to feed on their flesh. When they do so, they leave a recognizable trace on their victims that can be considered as a typical feature - they always eat the heart.

Another feature is that they are able to transform from a human form to werewolf form, which only happens under a full moon. It is speculated that they can only turn into a werewolf when they are asleep - as Sam and Dean were checking if they stopped Madison from turning into a werewolf ever again by staying in her appartement over a night under full moon, and she did not turn in to a werewolf, yet the next night she did turn into one.

In their werewolf form, they grow canine-like claws, teeth, and silver wolf-like eyes. Unlike folklore and movies, they don't grow wolf fur. As their bite is infectious (in this form, at least), they create more werewolves when biting typical humans.

After turning into their human form again, they don't retain any memory of the time when they were in their werewolf form.

Known Powers

 * Enhanced Strength - A werewolf's strength is greater then humans. They can rip flesh and bones with little force.
 * Infectous bite - A werewolf can turn anther person into a werewolf by biting them.
 * Enhanced Agility - Their agility is greater then humans.
 * Enhanced Speed - A werewolf can move supernaturally faster then both man and wolves.
 * Night Vision - All werewolve's can see in the dark.

Weaknesses
A werewolf's only weakness is silver, as they can be killed with a silver knife or bullet to the heart. It is possible that the Colt can be used against werewolf, as it is a weapon that can kill almost any supernatural creature.

Known Werewolves
There have been only two werewolves that have been on the series.
 * Kurt
 * Madison