Ravan - The Great King

Ravan - The Great King- yes u read it correct Ravan in general shown as a Rakshash but he was the great king and a great Devotee of the Lord Shiva and he is the author of the Rig veda , the only mistake he has done is to kidnap sita that too maya sita because he was one of the vijaya and jaya the gate keepers of the lord Narayana and he dint even touch Sita . the main reason for kidnapping sitawas only because laxman cut his sisters nose and ears and  and Ram on kidnapping Sita will act as the reason for Lord Narayana would kill ravana to give him shap vimoch andThe reason behind of Ram avatar was just too kill Ravan because Indra was worried that Ravan might capture the thrown and Ravan knowingly messed with vyshnavas (devotees of the Vishnu) so that Vishnu would come infront of him.

Ravan helped in fixing the right time for Rama to announce the war against him by which Rama could win the war and he would be killed. Ravan is not an evil but a great personality from whom we can learn a lot, knowing his life teaches you how one single mistake committed can end your life so Never Do anything bad or even think of doing bad. Ram Is good and Ravan is bad only in matter of sita but both are almost equal in the matter of knowledge and rituals and etc ... and one should know that Ravana Was the one for getting Athma Lingam to the Earth ... and He was a great guy that he just kidnapped Sita but dint even touch without her acceptance which is not known to any one learn all positives of all characters of the epics not the bad thing because once if they show bad only a man recognise the diff between both good and bad and the story of ramayana shows that never commit mistake wheather u might be too good in knowledge and in all aspects respect women and , good Always win over bad things it might be hard but definetly victory would be of good deeds and good cause not of evil intension.
Death of Ravana was not such easy task for Rama because of his great devotion he was given many wishes with Lord Brahma and Shiva.. To kill Ravana the 3 powers protecting Ravana should be disturbed then the Death of Ravana  is possible those 3 are 1.Ravana Brahma wife Madodari Devi's devotion .
2.The Jyothi (light) which would be always glowing in Lanka which should be violated then only it would off
3.the Amrutha bandam (imortality Fluid)which is in stomach of the Ravana
by disrupting the Pooja of Mandodari devi .by Spitting on the Akanda Jyothi by angadha and hanuman
and by aiming to stomach directly the Death of Ravana was possible.
Ravana death of only to show that DHARMA wins and ADHARMA Losses who ever it might be .
and Ravana does know his future of the Death.
Ravana is a Demon king with great morals but even tough knowing so many things one stupid thing kidnapping Sita lead him to death .
Ravana Kastam on dussera is done because as to show the victory of good over evil taughts and Jagan Mata gives a wish to Mandodhari w/o Ravan that he would alive in the form of Ravana Kastam till the end of the World.