Warring Natures

A character is a Half-Human Hybrid ('Human' being used loosely,) but the parent races of the two 'halves' are at war, or generally don't get along well. This can present a problem depending on how much the character looks like either one. If he looks nothing like one, he may be able to fit into the other group with ease. If he looks like a mixture of both, however, he likely won't be able to fit in with either group. At best, he'll be teased or shunned for it, possibly becoming an 'evil' loner. At worst, he'll be exiled or possibly even killed. This could even be the villain's Start of Darkness, if he's hated by both sides enough to plot the eradication of both.

If the two parent races are actually at war, the character will eventually be forced to choose a side to fight for. Depending on what they are, the choice may simply be between good and evil. Other times it may come down to 'the ones that shunned me' vs 'those that accepted me. Occaisionally, the decision is a difficult one, especially if he has friends from both sides. Depending on the cause of the mix, the character may be actively trying to become one side or the other, using the local Phlebotinum.

Related to Hunter of His Own Kind, for most hybrid characters. See also Tragic Mulatto. Depending on the situation, a Monsters Anonymous group may help reconcile or control the warring natures.

Examples of Warring Natures include:

Anime & Manga

Inuyasha is a half-demon, who demons tease and humans fear. He originally plans to use the Shikon Jewel to become a full-fledged demon, but never quite gets around to it.
Ichigo in Bleach, who's a human with Shinigami powers and a Super-Powered Evil Side that doesn't really get along with the rest of him. While he mostly manages to keep Shirosaki under control, his inner Hollow is just waiting for the first available opportunity to have a Rematch in the Center of the Mind and take over his body. And when that goal happens to align with his? Yes, Ichigo, I think we can safely say Orihime has been protected.

Literature

Changelings in The Dresden Files are half-human, half-fae. And when they grow up, they have to Choose which one they want to belong to and live their lives that way. But until then, they're mortals with fae features and traits.
Esmer of The Third Chronicles of Thomas Covenant is the son of a Haruchai (a race of super-strong Lawful Neutral warriors) and a merwife (Chaotic Neutral siren-like creatures). Hybrid Vigor gave Esmer extraordinary access to Earthpower. And the conflict between his haruchai and merwife natures make him batshit insane and potentially as harmful as any of Lord Foul's minions.
In the New Jedi Order, Tahiri has this problem after a failed attempt to turn her into a half-Jedi half-Yuuzhan Vong Super Soldier leaves her with two distinct personalities who are on opposite sides of the war. She finally resolves the issue near the end of the series, integrating both personalities to form, in effect, a completely new one with the strongest traits of both. And the she got Demoted to Extra.

Live Action TV

The villainous Scorpius in Farscape is half-Sebacean, half-Scarran, and most of villainous actions are due to his seeking to aid the Sebaceans against the Scarrans by getting whatever technology he can.
- This conflict is reflected more literally in his biology: Sebaceans have an extreme intolerance for heat, while Scarrans produce heat in huge amounts - thus, maintaining equilibrium is something that has always preoccupied Scorpius.
- A large part of his hatred of the Scarrans is due to having been created as a prototype for a hybrid slave-race. By raping his mother. And keeping her alive for the years-long pregnancy as she begged to be killed.
Michael of Stargate Atlantis. It doesn't work out very well for him.

Video Games

Toward the beginning of Boktai 2: Solar Boy Django, you get turned into a vampire. Although Django is eventually purified, he is stuck as half-vampire, half solar child. He continues his fight against undeads and immortals.
In World of Warcraft, there's at least one half-Draenei, half Orc NPC. He's a questgiver for both factions.
Seymour in Final Fantasy X? Half-human, half-Guado prince that was supposed to unite the two races, but winds up being ostracized by both because of his mixed race.

Webcomics

Glon, from Yet Another Fantasy Gamer Comic, is half-human, half-orc. He seems to be accepted by the monsters of Black Mountain, but that might be more out of respect and/or fear of his mother , orc matriarch Maula Bloodhand.

Other

Arc: Twilight of the Spirits had this as a driving plot - a pair of twins, Half Human Hybrids, had been divided at birth. One had grown up amongst the humans, and was fortunate enough to not have any visible signs of his demonic side (At least at first...), while the other one grew up amongst the Deimos, and was visibly half-human, causing him to be ridiculed as a 'Wannabe Deimos'. However, they both eventually rose to lead their respective factions in a war against their other side...
In Astro Boy, there was a cyborg (half human, half robot) that was detested by both the robots and the humans, back when they weren't on so good terms. He resented that, and plotted revenge.
In Rob Thurman's Cal and Niko series, Cal is half-human, half Auphe (really really really evil fairy). What are the most despised races in the world? Take a guess.