educational role of the custom of punishment in the qur'an

islam is a religion of mercy, but someone has blamed it as a   religion of violence. one reason for this accusation is frequency of words which referred to the suffering in the quran. the expressions referred to the punishment in the qur'an have some deferent meaning, such as: warning, as a traditional action for god, clarifying the sins which caused punishments in the day of judgment, and finally offering to some of worldly punishment. many verses of the qur'an regarding the punishment refer to the punishments in the  hereafter for disbelievers, as well as the polytheists. other kinds of these verses are about unjust rulers. lastly, the main goal of many of these punishment verses is reasonable and appropriate punishment for those who do crime and are offender, as well as for encouraging people to avod from doing crime and make society safely.             the method followed in this research is fundamental research and library based which analyze the verses containing punishment and tribulation. finally this study shows that punishment system in the qur'an is purposeful and lawful.