We can know the role of the Messiah in Islam,by comparing it with what the Jews of the first century believed regarding the Messiah.Meaning,what part of the Jewish escothology is in accordance with Islam.
again note,the Messiah has everything to do with the Jews.
The Messiah,will establish "The kingdom of God."Where the book of God,is the constitution.Where ,everything will be according to God's will.In other words,it will be the perfect society.Which wiil not be Second to any other society which was,which is,and which will be.
Secondly,as you mentioned,The annointed one,The Messiah will rid the world of evil.
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Why do you think the Jews rejected Jesus?
Because they reject that he is the Messiah.And tried to kill him.The Messiah cannot be killed,according to Old Testament.So when Christians say that Jesus died on the cross,they are rejecting their own faith.The Quran states that they did not kill Jesus.Because they Messiah cannot be killed.
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Jesus will fight the Jews when he comes back.Islam by far,makes the most sense.