Some examples:
Voldemort used a forbidden spell to split his soul into pieces so he could resurrect over and over, but he became less human each time. As the pieces he stored his soul in (horcruxes) were destroyed, so was his ability to return.
Nicholas Flamel and his wife used a potion to keep from aging. However, when they made the decision to no longer make the potion, they died.
The Peverell brothers used the Hallows, the Elder Wand, the Resurrection Stone, and the Cloak of Invisibility, to cheat death. In the end, they all still died. Ignotus Peverall was the only one of these three to go peacefully, but in the end, he realized he did not want to run from death (who was personified in this part of the story) forever.
AnswerThe ghosts and the dementors (well, the dementors aren't people, but monsters).See related questions for: 'Which characters die throughout the Harry Potter series?' If they aren't on that list; they didn't die.
There are hundreds of Harry Potter characters it would be impossible to list all that didn't die. Instead see related questions for a list of those who did die, anybody not on that list didn't die.
Hagrid does not die in the series. A lot of characters do, however.
no. but some of the characters die or have major or minor injures.
It was the middle of a war, people die in wars.
Lots of characters died, see related questions for more information.
Horcruxes or peices of your soul. Voldrmorts cause he cant die while he has some
Yes two: Albus Dumbledore and Lord Voldemort.
There a hundreds of Harry Potter character so it would be impossible to name all those who didn't die. Instead, please see related questions for a list of those who did die. Those not on the list, didn't die.
More than two main characters die. See related questions for more information.
There is no such character in Harry Potter.
There is no Niki in Harry Potter.