Not shown on screen; a character finds the ghosts of two little girls, and it is slowly revealed that their uncle molested them and killed them. The uncle is then punished, but it's not very satisfying - I wanted to see him get beat up. But he doesn't. The dad finds out what his brother did and is extremely upset. It's a very stressful scene and episode.
It's fairly mild, but three different characters are possessed by the villain, and whenever the villain makes itself known, it shows as snake/dragon scales on the characters face, neck, and hands.
In flashbacks, a character's mother leaves them, as a child, to die in the woods. They almost die, but are saved. Another character is also left to die as a child, and does; but this is not shown on-screen, but only recalled in a memory.
No, although it seems slightly implied that Yu Ri and Rang may have crushed the teens in a junkyard compactor for abusing a puppy. It is not shown on screen, but it seems heavily implied that they killed the teens.
The female lead's parents disappear when she is a child and it is strongly presumed they are dead, until later.
A side character's mother dies. SPOILER - Two brothers die.
there's implied canabalism in one episode, but nothing is shown explicitly. there's also some mentions of the foxes (in human form) eating people but again, nothing is shown explicitly.
Some teens are abusing a puppy. Yu Ri and Rang tie the teens up and then stab them with needles, and then play games with them that lead to more pain. It's implied that this ends with the teens being killed.
Not exactly vomit; when the villain makes people sick, it usually ends up with them "vomiting" up a large egg. It shows them gagging and choking it up on-screen.