Conversation so far:
How did Voldemort's character begin?
Rowling said Voldemort was invented as a nemesis for Harry Potter (the protagonist of the novels), and she intentionally did not flesh out Voldemort's backstory at first.
Why did rowling do that?
The basic idea [was that Harry] didn't know he was a wizard ...
And so then I kind of worked backwards from that position.
How else is voldemorts character developed?
When he was one year old, the most evil wizard for hundreds and hundreds of years attempted to kill him.
He killed Harry's parents, and then.
And then what did he do?
and then he tried to kill Harry--he tried to curse him.
...
Harry has to find out, before we find out.
And--so--but for some mysterious reason the curse.
Can you tell me more about the curse?
for some mysterious reason the curse didn't work on Harry.
So he's left with this lightning bolt shaped scar on his forehead and the curse rebounded upon the evil wizard.
what happens to the evil wizard?
In the second book, Rowling establishes that Voldemort hates non-pure-blood wizards, despite being a half-blood himself.
does anything else happen with voldemort in later books?
Rowling described Voldemort as a self-hating bully: "Well I think it is often the case that the biggest bullies take what they know to be their own defects.

Question: how is he a bully?
Self-contained rewrite: How is Voldemort a bully?