It might sound surprising but is a fact, as it is written in the Mahabharata itself.
The Kauravas had done many sins in their lifetime, yet they had attained the heaven after death.
So, does it mean that they did not get the punishment after death for their wrong doings?
The Parasara Smriti(the Dharma Sastra to be followed in Kali Yuga) talks about the impurities caused by birth & death in its chapter 3.
In this chapter there are few slokas that answer your question.
The following sloka says that the same higher heavens that Yogis & spiritual aspirants achieve after many sacrificial rites & and after performing many penances are achieved immediately by brave soldiers who meet with their death on the battleground. This sloka explains why the Kauravas, who all died in the battlefield, attained heaven inspite of doing many wrongs in their respective lifetimes.
Yam Yagnasanghaistapasa Cha Vipraha Swargairshino Vatra Yatha Yanti Chanena Yaantayebahi Tatra Viraha Praanaan Suyuddhena Paritayajantaha
Meaning-The regions which Brhaman aspirants after heavenly bliss reach by performing many sacrificial rites,and by austerities of various forms,the same seats of bliss are attained in an instant time by valorous men who meet their death while blamelessly fighting on a field of battle.
Yes, Yudhisthira saw Duryodhana in heaven and the Pandavas in hell. Yudhisthira was very upset at seeing Duryodhana having fun in heaven.
Indra explained to Yudhisthira, '…He who enjoys first the fruits of his good acts must afterwards endure Hell. He, on the other hand, who first endures Hell, must afterwards endure Heaven. He whose sinful acts are many, enjoys Heaven first. It is for this, O king, that desirous of doing thee good, I caused thee to be sent for having a view of Hell. Thou hadst, by a pretence, deceived Drona in the matter of his son. Thou hast, in consequence thereof, been shown Hell by deception. After the manner of thyself , Bhima and Arjuna, and Draupadi, have all been shown the place of sinners by an act of deception. Come, O chief of men, all of them have been cleansed of their sins. All those kings who have sided with thee and who have been slain in battle, have all attained to heaven....'
Mahabharata Swargarohanika Parva Section III
