Conversation so far:
What was Voldermort's character like?
Rowling described Voldemort as the most evil wizard for hundreds and hundreds of years.
What are some of Voldemort's character traits?
He is a psychopath and sadistic narcissist, with no conscience, regret, or empathy.

Question: How did they base decide what his character was going to be like?
Self-contained rewrite: What did JK Rowling base Voldemort's character on?