Why must Harry Potter die?

Answer 1

So when the author passes away they can bring the character Harry Potter back to life. Harry Potter had to die in the last book because when in the 4th book Voldemort took harry's blood to regain a body, he also took the protection lily potter gave harry when she died. so that meant that harry was immortal while voldemort lived. other than that, on the night vol tried to kill harry when he was 1, voldemort accidentally created another horcrux (as dumbledore puts it, his soul was so unstable, the stress of the rebounding curse caused part of his soul to shatter from the whole and attach itself to the only other living thing in the building - harry). so in the end when harry thinks hes destroyed all the other horcruxes, there is still one left in him. Then when he gets "killed" the part of voldemorts soul was killed, not him. so then the only part of voldemort left is in his body.

Answer 2

Not everyone wants to kill Harry. Just Lord Voldemort and his followers.

A prophecy made before Harry's birth said that a child born at the end of July would have the power to vanquish the Dark Lord - who would mark him as his equal. Not knowing the second part, Lord Voldemort tried to kill the Potter's who were put in hiding thus marking Harry (as Neville Longbottom also fit the profile). Eventually, the Potter's were betrayed, Voldemort killed Harry's parents, attempted to kill him and failed.

Voldemort still believed Harry was the only thing standing in the way of complete control and was determined to kill him because having a baby (and later a teenager) defeat him was humiliating.