Fully-Embraced Fiend

""I'm going to tell you a secret, but I think you already know it. Becoming a vampire doesn't change your personality; that's just a silly lie we tell to the newcomers to help them through their first few kills. "No! What's happening to me?! munch munch." Ha... It doesn't change the personality: it liberates it. A vampire is the only truly free man. All his darkness, all his excesses, they can run amok. He wants a girl? Take twenty. He wants a boy? Go ahead, just give the place a bit of a hose-down after. The world is his. The only limit is his imagination.""

- Herrick, Being Human (UK)

So your vampire hero or wolfman character is plagued by guilt, crippled by morals, and wants nothing more than to be mortal again. Naturally you need a foil, and that's where the Fully-Embraced Fiend comes in. Unlike the hero, this character is happy being a monster -- they like the immortality and the power, and has no problem putting the bite on anybody who doesn't like it.

Hey, just Be Yourself, right?

This character is not particularly evil; in fact, s/he is usually a friend of the hero, a source of (im)moral support and often a source of news and information on other fiends. They also won't hesitate to snark the hero on his lack of vampire pride or similar. These fiends usually have their own substantial, dedicated portion of fans among the audience.

However they still will tend to get these fans by the Sociopathic Hero or Magnificent Bastard route with a sort of sociopathy in how they view everybody else, moralistic characters being gutless morons who were afraid to take risks. They probably didn't start out like this, having gone through the Stages of Monster Grief before truly accepting their condition.

Vampire and werewolves, the sort of monster you can be turned into, are the typical target. If they are slightly evil they might be a Token Evil Teammate. Contrast with Transhuman Treachery where a character in the fight against such creatures gives in to the process that turns them into the enemy. Also contrast with Pro-Human Transhuman, where a character in the fight against such creatures resists the notion of superiority to humanity. Contrast with Monsters Anonymous, where the emphasis is on blending in with humanity... though the exact purpose to the blending in may vary.

Anime & Manga

 * In Hellsing, Alucard may be a psychotic vampire but he's still fighting for the good guys. Of course, the fact that the organization of "good guys" relies on a monster that routinely murders innocents for fun while doing his job is pointed out them. Usually by Alucard himself (because he finds it funny.)
 * He also likes to lecture younger, weaker vampires as he kills them. (Not because they've failed to embrace their nature, though; he's just that kinda guy.)
 * In Nightwalker, Cain has been a vampire for so long he can't really remember ever being anything else. He's not trying to kill or defeat the protagonists, he's just trying to convince his old lover to come back to him.

Comic Books

 * Inverted in Preacher (Comic Book) - Cassidy (a main character who is a vampire) is (outwardly) Well-Adjusted; one flashback issue features him meeting a vampire who read too much Anne Rice. His monstrous nature comes more from his addiction to heroin and his abuse of women.
 * This is Wolverine's relationship with Sabretooth, who's embraced his violent and feral instincts.
 * Cletus Kasady and Mac Gargan to Eddie Brock.

Film

 * In the original Buffy the Vampire Slayer movie, Luke Perry's buddy quickly becomes one of these to the still mortal Perry's character. Once best buds, he tries to convince him to turn too after he passes on being FOOD.

Literature

 * Lestat from Interview with the Vampire, as he teaches the protagonist to embrace being a vampire.
 * Reg Shoe from Discworld would count, as he is a zombie who holds undead pride meetings. Subverted in that he is really just a regular guy who happens to drop bits of himself now and again, and his attempts to fight for undead rights are an outlet for his desire to be a social reformer. He later joins the City Watch.
 * Henry Fitzroy from the Blood Books series by Tanya Huff.
 * Harry Potter gives us Fenrir Greyback, a cannibalistic werewolf with a taste for children -- transformed or not. He is the polar opposite of Remus Lupin, who hates being a werewolf and whose biggest flaw by Word of God is that he just wants to be liked.
 * By the end of the Dresden Files novel Turn Coat,  become one of these.

Live Action TV

 * LaCroix from Forever Knight but not so much Janette, since she, implying some dissatisfaction with the Vampire life even if she never mentioned it to Nick.
 * Josef Kostan, resident Deadpan Snarker and resulting Ensemble Darkhorse, on Moonlight.
 * Coraline Duvall as well, especially in the flashbacks. Not so much after her return, or so she claims.
 * Eric in True Blood who scoffs at Bill's drinking of the eponymous blood substitute and his remaining human tendencies.
 * Most vampires in the series bother little with restraint.
 * Herrick from Being Human (UK), who is always trying to get Mitchell to give up forsaking blood and get into a vampire world domination bid.
 * Similarly Tully wanted to convince George to embrace "the wolf" and act animalisticly. Particularly disturbing considering the depiction of the werewolf curse was treated on many occasions like an STD being passed on and the turning bite being like a rape. Eventually George got rid of him when he acted violently against his loved ones.
 * Veruca from Buffy the Vampire Slayer relishes in her werewolf side, believing it to be her true self and her human face just a disguise. She tries to get Oz to do the same.
 * Monroe and his group share Veruca's views.
 * In Season 6 Spike tries to take on this role for Buffy, convinced she Came Back Wrong after her death and resurrection. It turns out Buffy's just severely screwed up, and Spike's efforts to get her to embrace The Dark Side and run off with him only make things worse.
 * On the fifth season of Angel, Spike generally enjoys being a vamp -- even though he doesn't snack on humans, due to a combination of having a soul and most likely out of respect for Team Angel (though he'd never admit that). Angel, on the other hand, only broods about it.
 * Although they usually only appear for one episode, many of the informants to the Sanctuary crew do this,.
 * While Nikola Tesla embraces being a vampire, he doesn't go around killing people. That's Druitt's job. Tesla's vices include arrogance, excessive drinking of fine wines, and constant hitting on Helen, but he is rather reserved otherwise.
 * The Vampire Diaries: Vampires can actually shut off their feelings of guilt. This, along with living it up and making his brother's life a living Hell, is what Damon Salvatore does.
 * It's implied that he doesn't shut them off all the way, probably so he can enjoy it more..
 * Like in the Blood Books, Henry in Blood Ties embraces his vampiric nature. He seduces a girl every night to secretly snack on her while doing other stuff. He does give a speech to Vicki, including "someone has to die" in it. Coincidentally, the victim they are talking about is not dead, as Henry leads her to assume. He turned the girl. At the same time, Henry also has qualities of a Friendly Neighborhood Vampire.
 * Before cancellation, the show only had five vampires on it: Henry, Christina (Henry's lover/maker), Christina's other fledgling (who hates her), the previously-mentioned girl, and a Spanish nun turned by Henry during the Inquisition in return for freeing him (he thought it was a gift).
 * Erica is this to Sarah in My Babysitter's a Vampire.

Tabletop Games

 * Both Vampire: The Masquerade and Vampire: The Requiem feature a vampiric society that holds to the idea that you need to keep some measure of your Humanity, lest you fall to the Beast and become a mindless killer. Needless to say, their foils have other ideas. In Masquerade, the Sabbat is a society made up of vampires who believe they are superior to humanity, and have the right to rule over the "kine" as they wish (usually in a bloody and messy fashion). In Requiem, it's the covenant of Belial's Brood, who believe that the Beast is superior to paltry Humanity and perform atrocities to get closer to it.

Webcomics

 * Finas and Casimiro from Hanna Is Not a Boy's Name. They are quite used to being vampires, they have been for many years. They don't have particular side that they are on, they just do what's in their best interest and can be cordial (Finas keeps Cas in check) at times.
 * This eventually happened to the protagonist of Zebra Girl. Sandra, after years of fighting against her transformed-into-a-demon nature, finally gives in to the dark side. After causing a great deal of trouble, she is sucked into an alternate dimension where  How this all plays out it is yet to be seen.

Video Games

 * In Blood Omen, Vorador serves as one to the newly risen Kain.