Demogoblin
Real Name: Demogoblin is a true demon. Unless they're really powerful, demons tend to keep their names to themselves. He might answer to "Jason," since he and the Hobgoblin shared a body for several years.
First Appearance: Although the demon that would become Demogoblin possessed the Hobgoblin waaaay back during the Inferno crisis (Peter Parker, the Spectacular Spider-Man 147), it didn't obtain autonomy until Web of Spider-Man 85.
Died In: Despite technically not really what one could call "alive," Demogoblin nonetheless met a doom of sorts when he was first beaten up by his former host, then crushed by a falling church pillar, in Spider-Man 48. Most demons are notoriously un-crushable (and goblins have proved very difficult to kill even when they aren't demonic), so don't be too surprised if Demogoblin glides back into the Spidey books one of these days.
What's His Problem? When Jason Macendale offered his soul to N'astirh in exchange for power, N'astirh rejected the soul as being way too icky even for him, but went ahead and had a decidedly-unbalanced demon possess Macendale anyway. The two co-habited Macendale's body for some time, fighting an intense mental and physical battle for control. During a battle with Spider-Man where Macendale flipped uncontrollably between his human and his demonic form, the demon ripped free of Macendale's body. Sundered both from his mortal host and from the others of his other-worldly sect (who, according to him, had banded together to rid the world of sinners), Demogoblin went more insane than your average embodiment of evil and decided he would only find redemption through the blood sacrifice of others. He ended up being a really confused religious fanatic who couldn't decide if his holy mission involved punishing every "sinner" on Earth or just meant eradicating all traces of demonic blood from the planet.
Powers: Once casting off Macendale's mortal coil, Demogoblin continued to use many of the paraphernalia associated with the various Goblins over the years--except that Demogoblin formed his pumpkin bombs and gliders out of thin air. His accruements tended to be coated in fire and reeked of brimstone.
Heroes He Keeps Running Into: Spider-Man took responsibility for Demogoblin (more than that cad Macendale ever did), and repeatedly tried to corral the demon. Demogoblin received the chance to pound on multiple super-heroes when he tangled with Venom, Ghost Rider and Johnny Blaze all at once; a nice practice run for Maximum Carnage, where he got the opportunity to punish just about every hero in New York.
Favorite Quote: "I ... reject your twisted gospel, Carnage! The universe is nothing but pattern and plan! A plan veiled from us by the sins of a corrupted world!" (Spectacular Spider-Man 201, as Carnage's anarchist philosophy gets on Demogoblin's nerves).
People Who Think He's Not So Bad: Hey, this guy is a demon! His constant search for divine forgiveness precluded Demogoblin from finding acceptance amongst his human victims. He didn't really get along with his sometimes partner, Spider-Man's mindless Doppleganger. His former host Macendale hated him so much he passed up a chance to off Spider-Man for a clear shot at his ex-tenant. Heck, despite being a psychotic killer, Demogoblin couldn't even get along with Carnage, who likes working with other psychotic killers!
Most Despicable Act: Demogoblin's one-demon crusade to rid the world of sinners imperiled all he met except the youngest children. He routinely butchered people who dealt drugs, got into fist fights, or just looked at him wrong ... because, as far as he was concerned, everyone was a sinner.