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.

Question: And then what did he do?
Self-contained rewrite: After Voldemort attempted to kill Harry and killed Harry's parents, what did Voldemort do next?