This is enough to understand that Ravana was not a bad man.
*1.* He kept Sita in Lanka for years, but he never even touched her. Would a bad man do that? In the end, it was Rama who abandoned Sita in the forest.
*2.* His 10 heads were not real heads. It meant he had mastered 10 sciences. He made Lanka a golden city. He was a scientist.
*3.* He went to war because Lakshmana cut off his sister Shurpanakha's nose. That was not revenge, that was a brother's love.
*4.* Even when he was dying, Rama asked him for knowledge. Would a god ask a villain for knowledge?
*5.* According to the Sri Lankan story, Sita was his own daughter. Is it kidnapping when a father brings his daughter to save her?
History was written by Rama's side because he won. That's why Ravana became the villain. In reality, Ravana was a great king who loved his country, his sister, and his daughter.