Werekin

Werekin are a particularly brutal breed of shape-shifting demons which take the form of various predatory animals, albeit a humanoid beast version. They are often described as being more dangerous than even vampires due to their similar levels of resilience and superior strength.

Werewolves
Also called Wolfmen or Lycans, Werewolves are the most well-known form of werekin.

History
Before the days of Ultimate or even The Dawn, Werewolves were plentiful. In Dawn, when he and a teenage Walter face off against The Captain, Alucard recognizes what he is immediately, indicating he's run into their kind before. Given the Hellsing Organization's mission and purpose, it is possible that they were fully or partially responsible for the near extinction of Werewolf-kind.

Alucard remarks he thought their species had been defeated, implying that The Captain is last of his kind.

Abilities
In general, Werewolves appear to be stronger than Vampires, even the modified vampire Alucard. What they can naturally do and not is unclear, as it is possible the Doctor tampered with The Captain's biology, making him modified like Alucard.
 * Superhuman Strength
 * Superhuman Reflexes
 * Thick Skin
 * Wolf Form

Weakness
The only known weakness werewolves have is Silver. Holy water, crosses, and other ceremonial items are completely ineffective against them.