Ravana was born as Dashanana, demon with 10 heads, to Rishi Vishrava and demon princess Kaikesi. He had two brothers, Kubera and Vibhishan.
Ravan, because of his greed, decided to get more Vardans from the Tridev(Brahma, Vishnu , Mahesh) and went to Kailash Parvat to please Lord Shiva.
Time flew by, and after the incident Ravan became more and more unjust to the ones around him. However, he remained fair to his people in the kingdom of Lanka.
First aspect that people saw was that the demon-king had a lot of arrogance which defeated his decision-making skills.